/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.text;

import java.io.IOException;
import java.io.Reader;
import java.io.Serializable;
import java.io.Writer;
import java.nio.CharBuffer;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;

import org.apache.commons.lang3.ArrayFill;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Strings;
import org.apache.commons.lang3.builder.Builder;

/**
 * Builds a string from constituent parts providing a more flexible and powerful API
 * than StringBuffer.
 * <p>
 * The main differences from StringBuffer/StringBuilder are:
 * </p>
 * <ul>
 * <li>Not synchronized</li>
 * <li>Not final</li>
 * <li>Subclasses have direct access to character array</li>
 * <li>Additional methods
 *  <ul>
 *   <li>appendWithSeparators - adds an array of values, with a separator</li>
 *   <li>appendPadding - adds a length padding characters</li>
 *   <li>appendFixedLength - adds a fixed width field to the builder</li>
 *   <li>toCharArray/getChars - simpler ways to get a range of the character array</li>
 *   <li>delete - delete char or string</li>
 *   <li>replace - search and replace for a char or string</li>
 *   <li>leftString/rightString/midString - substring without exceptions</li>
 *   <li>contains - whether the builder contains a char or string</li>
 *   <li>size/clear/isEmpty - collections style API methods</li>
 *  </ul>
 * </li>
 * <li>Views
 *  <ul>
 *   <li>asTokenizer - uses the internal buffer as the source of a StrTokenizer</li>
 *   <li>asReader - uses the internal buffer as the source of a Reader</li>
 *   <li>asWriter - allows a Writer to write directly to the internal buffer</li>
 *  </ul>
 * </li>
 * </ul>
 * <p>
 * The aim has been to provide an API that mimics very closely what StringBuffer
 * provides, but with additional methods. It should be noted that some edge cases,
 * with invalid indices or null input, have been altered - see individual methods.
 * The biggest of these changes is that by default, null will not output the text
 * 'null'. This can be controlled by a property, {@link #setNullText(String)}.
 * </p>
 * <p>
 * Prior to 3.0, this class implemented Cloneable but did not implement the
 * clone method so could not be used. From 3.0 onwards it no longer implements
 * the interface.
 * </p>
 *
 * @since 2.2
 * @deprecated As of <a href="https://commons.apache.org/proper/commons-lang/changes-report.html#a3.6">3.6</a>, use Apache Commons Text
 * <a href="https://commons.apache.org/proper/commons-text/javadocs/api-release/org/apache/commons/text/TextStringBuilder.html">
 * TextStringBuilder</a>.
 */
@Deprecated
public class StrBuilder implements CharSequence, Appendable, Serializable, Builder<String> {

    /**
     * Inner class to allow StrBuilder to operate as a reader.
     */
    final class StrBuilderReader extends Reader {

        /** The current stream position. */
        private int pos;

        /** The last mark position. */
        private int mark;

        /**
         * Default constructor.
         */
        StrBuilderReader() {
        }

        /** {@inheritDoc} */
        @Override
        public void close() {
            // do nothing
        }

        /** {@inheritDoc} */
        @Override
        public void mark(final int readAheadLimit) {
            mark = pos;
        }

        /** {@inheritDoc} */
        @Override
        public boolean markSupported() {
            return true;
        }

        /** {@inheritDoc} */
        @Override
        public int read() {
            if (!ready()) {
                return -1;
            }
            return charAt(pos++);
        }

        /** {@inheritDoc} */
        @Override
        public int read(final char[] b, final int off, int len) {
            if (off < 0 || len < 0 || off > b.length ||
                    off + len > b.length || off + len < 0) {
                throw new IndexOutOfBoundsException();
            }
            if (len == 0) {
                return 0;
            }
            if (pos >= size()) {
                return -1;
            }
            if (pos + len > size()) {
                len = size() - pos;
            }
            StrBuilder.this.getChars(pos, pos + len, b, off);
            pos += len;
            return len;
        }

        /** {@inheritDoc} */
        @Override
        public boolean ready() {
            return pos < size();
        }

        /** {@inheritDoc} */
        @Override
        public void reset() {
            pos = mark;
        }

        /** {@inheritDoc} */
        @Override
        public long skip(long n) {
            if (pos + n > size()) {
                n = size() - pos;
            }
            if (n < 0) {
                return 0;
            }
            pos = Math.addExact(pos, Math.toIntExact(n));
            return n;
        }
    }

    /**
     * Inner class to allow StrBuilder to operate as a tokenizer.
     */
    final class StrBuilderTokenizer extends StrTokenizer {

        /**
         * Default constructor.
         */
        StrBuilderTokenizer() {
        }

        /** {@inheritDoc} */
        @Override
        public String getContent() {
            final String str = super.getContent();
            if (str == null) {
                return StrBuilder.this.toString();
            }
            return str;
        }

        /** {@inheritDoc} */
        @Override
        protected List<String> tokenize(final char[] chars, final int offset, final int count) {
            if (chars == null) {
                return super.tokenize(StrBuilder.this.buffer, 0, StrBuilder.this.size());
            }
            return super.tokenize(chars, offset, count);
        }
    }

    /**
     * Inner class to allow StrBuilder to operate as a writer.
     */
    final class StrBuilderWriter extends Writer {

        /**
         * Default constructor.
         */
        StrBuilderWriter() {
        }

        /** {@inheritDoc} */
        @Override
        public void close() {
            // do nothing
        }

        /** {@inheritDoc} */
        @Override
        public void flush() {
            // do nothing
        }

        /** {@inheritDoc} */
        @Override
        public void write(final char[] cbuf) {
            StrBuilder.this.append(cbuf);
        }

        /** {@inheritDoc} */
        @Override
        public void write(final char[] cbuf, final int off, final int len) {
            StrBuilder.this.append(cbuf, off, len);
        }

        /** {@inheritDoc} */
        @Override
        public void write(final int c) {
            StrBuilder.this.append((char) c);
        }

        /** {@inheritDoc} */
        @Override
        public void write(final String str) {
            StrBuilder.this.append(str);
        }

        /** {@inheritDoc} */
        @Override
        public void write(final String str, final int off, final int len) {
            StrBuilder.this.append(str, off, len);
        }
    }

    /**
     * The extra capacity for new builders.
     */
    static final int CAPACITY = 32;

    /**
     * Required for serialization support.
     *
     * @see java.io.Serializable
     */
    private static final long serialVersionUID = 7628716375283629643L;

    /** Internal data storage. */
    protected char[] buffer; // TODO make private?

    /** Current size of the buffer. */
    protected int size; // TODO make private?

    /**
     * The new line, {@code null} means use the system default from {@link System#lineSeparator()}.
     */
    private String newLine;

    /** The null text. */
    private String nullText;

    /**
     * Constructor that creates an empty builder initial capacity 32 characters.
     */
    public StrBuilder() {
        this(CAPACITY);
    }

    /**
     * Constructor that creates an empty builder the specified initial capacity.
     *
     * @param initialCapacity  The initial capacity, zero or less will be converted to 32.
     */
    public StrBuilder(int initialCapacity) {
        if (initialCapacity <= 0) {
            initialCapacity = CAPACITY;
        }
        buffer = new char[initialCapacity];
    }

    /**
     * Constructor that creates a builder from the string, allocating
     * 32 extra characters for growth.
     *
     * @param str  The string to copy, null treated as blank string.
     */
    public StrBuilder(final String str) {
        if (str == null) {
            buffer = new char[CAPACITY];
        } else {
            buffer = new char[str.length() + CAPACITY];
            append(str);
        }
    }

    /**
     * Appends a boolean value to the string builder.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final boolean value) {
        if (value) {
            ensureCapacity(size + 4);
            buffer[size++] = 't';
            buffer[size++] = 'r';
            buffer[size++] = 'u';
        } else {
            ensureCapacity(size + 5);
            buffer[size++] = 'f';
            buffer[size++] = 'a';
            buffer[size++] = 'l';
            buffer[size++] = 's';
        }
        buffer[size++] = 'e';
        return this;
    }

    /**
     * Appends a char value to the string builder.
     *
     * @param ch  The value to append.
     * @return {@code this} instance.
     * @since 3.0
     */
    @Override
    public StrBuilder append(final char ch) {
        final int len = length();
        ensureCapacity(len + 1);
        buffer[size++] = ch;
        return this;
    }

    /**
     * Appends a char array to the string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param chars  The char array to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final char[] chars) {
        if (chars == null) {
            return appendNull();
        }
        final int strLen = chars.length;
        if (strLen > 0) {
            final int len = length();
            ensureCapacity(len + strLen);
            System.arraycopy(chars, 0, buffer, len, strLen);
            size += strLen;
        }
        return this;
    }

    /**
     * Appends a char array to the string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param chars  The char array to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     */
    public StrBuilder append(final char[] chars, final int startIndex, final int length) {
        if (chars == null) {
            return appendNull();
        }
        if (startIndex < 0 || startIndex > chars.length) {
            throw new StringIndexOutOfBoundsException("Invalid startIndex: " + startIndex);
        }
        if (length < 0 || startIndex + length > chars.length) {
            throw new StringIndexOutOfBoundsException("Invalid length: " + length);
        }
        if (length > 0) {
            final int len = length();
            ensureCapacity(len + length);
            System.arraycopy(chars, startIndex, buffer, len, length);
            size += length;
        }
        return this;
    }

    /**
     * Appends the contents of a char buffer to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param buf  The char buffer to append.
     * @return {@code this} instance.
     * @since 3.4
     */
    public StrBuilder append(final CharBuffer buf) {
        if (buf == null) {
            return appendNull();
        }
        if (buf.hasArray()) {
            final int length = buf.remaining();
            final int len = length();
            ensureCapacity(len + length);
            System.arraycopy(buf.array(), buf.arrayOffset() + buf.position(), buffer, len, length);
            size += length;
        } else {
            append(buf.toString());
        }
        return this;
    }

    /**
     * Appends the contents of a char buffer to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param buf  The char buffer to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 3.4
     */
    public StrBuilder append(final CharBuffer buf, final int startIndex, final int length) {
        if (buf == null) {
            return appendNull();
        }
        if (buf.hasArray()) {
            final int totalLength = buf.remaining();
            if (startIndex < 0 || startIndex > totalLength) {
                throw new StringIndexOutOfBoundsException("startIndex must be valid");
            }
            if (length < 0 || startIndex + length > totalLength) {
                throw new StringIndexOutOfBoundsException("length must be valid");
            }
            final int len = length();
            ensureCapacity(len + length);
            System.arraycopy(buf.array(), buf.arrayOffset() + buf.position() + startIndex, buffer, len, length);
            size += length;
        } else {
            append(buf.toString(), startIndex, length);
        }
        return this;
    }

    /**
     * Appends a CharSequence to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param seq  The CharSequence to append.
     * @return {@code this} instance.
     * @since 3.0
     */
    @Override
    public StrBuilder append(final CharSequence seq) {
        if (seq == null) {
            return appendNull();
        }
        if (seq instanceof StrBuilder) {
            return append((StrBuilder) seq);
        }
        if (seq instanceof StringBuilder) {
            return append((StringBuilder) seq);
        }
        if (seq instanceof StringBuffer) {
            return append((StringBuffer) seq);
        }
        if (seq instanceof CharBuffer) {
            return append((CharBuffer) seq);
        }
        return append(seq.toString());
    }

    /**
     * Appends part of a CharSequence to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param seq  The CharSequence to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 3.0
     */
    @Override
    public StrBuilder append(final CharSequence seq, final int startIndex, final int length) {
        if (seq == null) {
            return appendNull();
        }
        return append(seq.toString(), startIndex, length);
    }

    /**
     * Appends a double value to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final double value) {
        return append(String.valueOf(value));
    }

    /**
     * Appends a float value to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final float value) {
        return append(String.valueOf(value));
    }

    /**
     * Appends an int value to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final int value) {
        return append(String.valueOf(value));
    }

    /**
     * Appends a long value to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final long value) {
        return append(String.valueOf(value));
    }

    /**
     * Appends an object to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param obj  The object to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final Object obj) {
        if (obj == null) {
            return appendNull();
        }
        if (obj instanceof CharSequence) {
            return append((CharSequence) obj);
        }
        return append(obj.toString());
    }

    /**
     * Appends another string builder to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string builder to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final StrBuilder str) {
        if (str == null) {
            return appendNull();
        }
        final int strLen = str.length();
        if (strLen > 0) {
            final int len = length();
            ensureCapacity(len + strLen);
            System.arraycopy(str.buffer, 0, buffer, len, strLen);
            size += strLen;
        }
        return this;
    }

    /**
     * Appends part of a string builder to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     */
    public StrBuilder append(final StrBuilder str, final int startIndex, final int length) {
        if (str == null) {
            return appendNull();
        }
        if (startIndex < 0 || startIndex > str.length()) {
            throw new StringIndexOutOfBoundsException("startIndex must be valid");
        }
        if (length < 0 || startIndex + length > str.length()) {
            throw new StringIndexOutOfBoundsException("length must be valid");
        }
        if (length > 0) {
            final int len = length();
            ensureCapacity(len + length);
            str.getChars(startIndex, startIndex + length, buffer, len);
            size += length;
        }
        return this;
    }

    /**
     * Appends a string to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final String str) {
        if (str == null) {
            return appendNull();
        }
        final int strLen = str.length();
        if (strLen > 0) {
            final int len = length();
            ensureCapacity(len + strLen);
            str.getChars(0, strLen, buffer, len);
            size += strLen;
        }
        return this;
    }

    /**
     * Appends part of a string to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     */
    public StrBuilder append(final String str, final int startIndex, final int length) {
        if (str == null) {
            return appendNull();
        }
        if (startIndex < 0 || startIndex > str.length()) {
            throw new StringIndexOutOfBoundsException("startIndex must be valid");
        }
        if (length < 0 || startIndex + length > str.length()) {
            throw new StringIndexOutOfBoundsException("length must be valid");
        }
        if (length > 0) {
            final int len = length();
            ensureCapacity(len + length);
            str.getChars(startIndex, startIndex + length, buffer, len);
            size += length;
        }
        return this;
    }

    /**
     * Calls {@link String#format(String, Object...)} and appends the result.
     *
     * @param format The format string.
     * @param objs The objects to use in the format string.
     * @return {@code this} to enable chaining.
     * @see String#format(String, Object...)
     * @since 3.2
     */
    public StrBuilder append(final String format, final Object... objs) {
        return append(String.format(format, objs));
    }

    /**
     * Appends a string buffer to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string buffer to append.
     * @return {@code this} instance.
     */
    public StrBuilder append(final StringBuffer str) {
        if (str == null) {
            return appendNull();
        }
        final int strLen = str.length();
        if (strLen > 0) {
            final int len = length();
            ensureCapacity(len + strLen);
            str.getChars(0, strLen, buffer, len);
            size += strLen;
        }
        return this;
    }

    /**
     * Appends part of a string buffer to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     */
    public StrBuilder append(final StringBuffer str, final int startIndex, final int length) {
        if (str == null) {
            return appendNull();
        }
        if (startIndex < 0 || startIndex > str.length()) {
            throw new StringIndexOutOfBoundsException("startIndex must be valid");
        }
        if (length < 0 || startIndex + length > str.length()) {
            throw new StringIndexOutOfBoundsException("length must be valid");
        }
        if (length > 0) {
            final int len = length();
            ensureCapacity(len + length);
            str.getChars(startIndex, startIndex + length, buffer, len);
            size += length;
        }
        return this;
    }

    /**
     * Appends a StringBuilder to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str The StringBuilder to append.
     * @return {@code this} instance.
     * @since 3.2
     */
    public StrBuilder append(final StringBuilder str) {
        if (str == null) {
            return appendNull();
        }
        final int strLen = str.length();
        if (strLen > 0) {
            final int len = length();
            ensureCapacity(len + strLen);
            str.getChars(0, strLen, buffer, len);
            size += strLen;
        }
        return this;
    }

    /**
     * Appends part of a StringBuilder to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str The StringBuilder to append.
     * @param startIndex The start index, inclusive, must be valid.
     * @param length The length to append, must be valid.
     * @return {@code this} instance.
     * @since 3.2
     */
    public StrBuilder append(final StringBuilder str, final int startIndex, final int length) {
        if (str == null) {
            return appendNull();
        }
        if (startIndex < 0 || startIndex > str.length()) {
            throw new StringIndexOutOfBoundsException("startIndex must be valid");
        }
        if (length < 0 || startIndex + length > str.length()) {
            throw new StringIndexOutOfBoundsException("length must be valid");
        }
        if (length > 0) {
            final int len = length();
            ensureCapacity(len + length);
            str.getChars(startIndex, startIndex + length, buffer, len);
            size += length;
        }
        return this;
    }

    /**
     * Appends each item in an iterable to the builder without any separators.
     * Appending a null iterable will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param iterable  The iterable to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendAll(final Iterable<?> iterable) {
        if (iterable != null) {
            iterable.forEach(this::append);
        }
        return this;
    }

    /**
     * Appends each item in an iterator to the builder without any separators.
     * Appending a null iterator will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param it  The iterator to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendAll(final Iterator<?> it) {
        if (it != null) {
            it.forEachRemaining(this::append);
        }
        return this;
    }

    /**
     * Appends each item in an array to the builder without any separators.
     * Appending a null array will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param <T>  the element type.
     * @param array  The array to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public <T> StrBuilder appendAll(@SuppressWarnings("unchecked") final T... array) {
        /*
         * @SuppressWarnings used to hide warning about vararg usage. We cannot
         * use @SafeVarargs, since this method is not final. Using @SuppressWarnings
         * is fine, because it isn't inherited by subclasses, so each subclass must
         * vouch for itself whether its use of 'array' is safe.
         */
        if (ArrayUtils.isNotEmpty(array)) {
            for (final Object element : array) {
                append(element);
            }
        }
        return this;
    }

    /**
     * Appends an object to the builder padding on the left to a fixed width.
     * The {@code String.valueOf} of the {@code int} value is used.
     * If the formatted value is larger than the length, the left-hand side is lost.
     *
     * @param value  The value to append.
     * @param width  The fixed field width, zero or negative has no effect.
     * @param padChar  The pad character to use.
     * @return {@code this} instance.
     */
    public StrBuilder appendFixedWidthPadLeft(final int value, final int width, final char padChar) {
        return appendFixedWidthPadLeft(String.valueOf(value), width, padChar);
    }

    /**
     * Appends an object to the builder padding on the left to a fixed width.
     * The {@code toString} of the object is used.
     * If the object is larger than the length, the left-hand side is lost.
     * If the object is null, the null text value is used.
     *
     * @param obj  The object to append, null uses null text.
     * @param width  The fixed field width, zero or negative has no effect.
     * @param padChar  The pad character to use.
     * @return {@code this} instance.
     */
    public StrBuilder appendFixedWidthPadLeft(final Object obj, final int width, final char padChar) {
        if (width > 0) {
            ensureCapacity(size + width);
            String str = ObjectUtils.toString(obj, this::getNullText);
            if (str == null) {
                str = StringUtils.EMPTY;
            }
            final int strLen = str.length();
            if (strLen >= width) {
                str.getChars(strLen - width, strLen, buffer, size);
            } else {
                final int padLen = width - strLen;
                final int toIndex = size + padLen;
                Arrays.fill(buffer, size, toIndex, padChar);
                str.getChars(0, strLen, buffer, toIndex);
            }
            size += width;
        }
        return this;
    }

    /**
     * Appends an object to the builder padding on the right to a fixed length.
     * The {@code String.valueOf} of the {@code int} value is used.
     * If the object is larger than the length, the right-hand side is lost.
     *
     * @param value  The value to append.
     * @param width  The fixed field width, zero or negative has no effect.
     * @param padChar  The pad character to use.
     * @return {@code this} instance.
     */
    public StrBuilder appendFixedWidthPadRight(final int value, final int width, final char padChar) {
        return appendFixedWidthPadRight(String.valueOf(value), width, padChar);
    }

    /**
     * Appends an object to the builder padding on the right to a fixed length.
     * The {@code toString} of the object is used.
     * If the object is larger than the length, the right-hand side is lost.
     * If the object is null, null text value is used.
     *
     * @param obj  The object to append, null uses null text.
     * @param width  The fixed field width, zero or negative has no effect.
     * @param padChar  The pad character to use.
     * @return {@code this} instance.
     */
    public StrBuilder appendFixedWidthPadRight(final Object obj, final int width, final char padChar) {
        if (width > 0) {
            ensureCapacity(size + width);
            String str = ObjectUtils.toString(obj, this::getNullText);
            if (str == null) {
                str = StringUtils.EMPTY;
            }
            final int strLen = str.length();
            if (strLen >= width) {
                str.getChars(0, width, buffer, size);
            } else {
                str.getChars(0, strLen, buffer, size);
                final int fromIndex = size + strLen;
                Arrays.fill(buffer, fromIndex, fromIndex + width - strLen, padChar);
            }
            size += width;
        }
        return this;
    }

    /**
     * Appends a boolean value followed by a new line to the string builder.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final boolean value) {
        return append(value).appendNewLine();
    }

    /**
     * Appends a char value followed by a new line to the string builder.
     *
     * @param ch  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final char ch) {
        return append(ch).appendNewLine();
    }

    /**
     * Appends a char array followed by a new line to the string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param chars  The char array to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final char[] chars) {
        return append(chars).appendNewLine();
    }

    /**
     * Appends a char array followed by a new line to the string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param chars  The char array to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final char[] chars, final int startIndex, final int length) {
        return append(chars, startIndex, length).appendNewLine();
    }

    /**
     * Appends a double value followed by a new line to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final double value) {
        return append(value).appendNewLine();
    }

    /**
     * Appends a float value followed by a new line to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final float value) {
        return append(value).appendNewLine();
    }

    /**
     * Appends an int value followed by a new line to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final int value) {
        return append(value).appendNewLine();
    }

    /**
     * Appends a long value followed by a new line to the string builder using {@code String.valueOf}.
     *
     * @param value  The value to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final long value) {
        return append(value).appendNewLine();
    }

    /**
     * Appends an object followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param obj  The object to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final Object obj) {
        return append(obj).appendNewLine();
    }

    /**
     * Appends another string builder followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string builder to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final StrBuilder str) {
        return append(str).appendNewLine();
    }

    /**
     * Appends part of a string builder followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final StrBuilder str, final int startIndex, final int length) {
        return append(str, startIndex, length).appendNewLine();
    }

    /**
     * Appends a string followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final String str) {
        return append(str).appendNewLine();
    }

    /**
     * Appends part of a string followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final String str, final int startIndex, final int length) {
        return append(str, startIndex, length).appendNewLine();
    }

    /**
     * Calls {@link String#format(String, Object...)} and appends the result.
     *
     * @param format The format string.
     * @param objs The objects to use in the format string.
     * @return {@code this} to enable chaining.
     * @see String#format(String, Object...)
     * @since 3.2
     */
    public StrBuilder appendln(final String format, final Object... objs) {
        return append(format, objs).appendNewLine();
    }

    /**
     * Appends a string buffer followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string buffer to append.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final StringBuffer str) {
        return append(str).appendNewLine();
    }

    /**
     * Appends part of a string buffer followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendln(final StringBuffer str, final int startIndex, final int length) {
        return append(str, startIndex, length).appendNewLine();
    }

    /**
     * Appends a string builder followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string builder to append.
     * @return {@code this} instance.
     * @since 3.2
     */
    public StrBuilder appendln(final StringBuilder str) {
        return append(str).appendNewLine();
    }

    /**
     * Appends part of a string builder followed by a new line to this string builder.
     * Appending null will call {@link #appendNull()}.
     *
     * @param str  The string builder to append.
     * @param startIndex  The start index, inclusive, must be valid.
     * @param length  The length to append, must be valid.
     * @return {@code this} instance.
     * @since 3.2
     */
    public StrBuilder appendln(final StringBuilder str, final int startIndex, final int length) {
        return append(str, startIndex, length).appendNewLine();
    }

    /**
     * Appends this builder's new line string to this builder.
     * <p>
     * By default, the new line is the system default from {@link System#lineSeparator()}.
     * </p>
     * <p>
     * The new line string can be changed using {@link #setNewLineText(String)}. For example, you can use this to force the output to always use Unix line
     * endings even when on Windows.
     * </p>
     *
     * @return {@code this} instance.
     * @see #getNewLineText()
     * @see #setNewLineText(String)
     */
    public StrBuilder appendNewLine() {
        if (newLine == null)  {
            append(System.lineSeparator());
            return this;
        }
        return append(newLine);
    }

    /**
     * Appends the text representing {@code null} to this string builder.
     *
     * @return {@code this} instance.
     */
    public StrBuilder appendNull() {
        if (nullText == null)  {
            return this;
        }
        return append(nullText);
    }

    /**
     * Appends the pad character to the builder the specified number of times.
     *
     * @param length  The length to append, negative means no append.
     * @param padChar  The character to append.
     * @return {@code this} instance.
     */
    public StrBuilder appendPadding(final int length, final char padChar) {
        if (length >= 0) {
            ensureCapacity(size + length);
            for (int i = 0; i < length; i++) {
                buffer[size++] = padChar;
            }
        }
        return this;
    }

    /**
     * Appends a separator if the builder is currently non-empty.
     * The separator is appended using {@link #append(char)}.
     * <p>
     * This method is useful for adding a separator each time around the
     * loop except the first.
     * </p>
     * <pre>
     * for (Iterator it = list.iterator(); it.hasNext(); ) {
     *   appendSeparator(',');
     *   append(it.next());
     * }
     * </pre>
     * <p>
     * Note that for this simple example, you should use
     * {@link #appendWithSeparators(Iterable, String)}.
     * </p>
     *
     * @param separator  The separator to use.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendSeparator(final char separator) {
        if (isNotEmpty()) {
            append(separator);
        }
        return this;
    }

    /**
     * Append one of both separators to the builder
     * If the builder is currently empty it will append the defaultIfEmpty-separator
     * Otherwise it will append the standard-separator
     *
     * The separator is appended using {@link #append(char)}.
     *
     * @param standard The separator if builder is not empty.
     * @param defaultIfEmpty The separator if builder is empty.
     * @return {@code this} instance.
     * @since 2.5
     */
    public StrBuilder appendSeparator(final char standard, final char defaultIfEmpty) {
        if (isNotEmpty()) {
            append(standard);
        } else {
            append(defaultIfEmpty);
        }
        return this;
    }

    /**
     * Appends a separator to the builder if the loop index is greater than zero.
     * The separator is appended using {@link #append(char)}.
     * <p>
     * This method is useful for adding a separator each time around the
     * loop except the first.
     * </p>
     * <pre>{@code
     * for (int i = 0; i < list.size(); i++) {
     *   appendSeparator(",", i);
     *   append(list.get(i));
     * }
     * }
     * </pre>
     * <p>
     * Note that for this simple example, you should use
     * {@link #appendWithSeparators(Iterable, String)}.
     * </p>
     *
     * @param separator  The separator to use.
     * @param loopIndex  The loop index.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendSeparator(final char separator, final int loopIndex) {
        if (loopIndex > 0) {
            append(separator);
        }
        return this;
    }

    /**
     * Appends a separator if the builder is currently non-empty.
     * Appending a null separator will have no effect.
     * The separator is appended using {@link #append(String)}.
     * <p>
     * This method is useful for adding a separator each time around the
     * loop except the first.
     * </p>
     * <pre>
     * for (Iterator it = list.iterator(); it.hasNext(); ) {
     *   appendSeparator(",");
     *   append(it.next());
     * }
     * </pre>
     * <p>
     * Note that for this simple example, you should use
     * {@link #appendWithSeparators(Iterable, String)}.
     * </p>
     *
     * @param separator  The separator to use, null means no separator.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendSeparator(final String separator) {
        return appendSeparator(separator, null);
    }

    /**
     * Appends a separator to the builder if the loop index is greater than zero.
     * Appending a null separator will have no effect.
     * The separator is appended using {@link #append(String)}.
     * <p>
     * This method is useful for adding a separator each time around the
     * loop except the first.
     * </p>
     * <pre>{@code
     * for (int i = 0; i < list.size(); i++) {
     *   appendSeparator(",", i);
     *   append(list.get(i));
     * }
     * }</pre>
     * <p>
     * Note that for this simple example, you should use
     * {@link #appendWithSeparators(Iterable, String)}.
     * </p>
     *
     * @param separator  The separator to use, null means no separator.
     * @param loopIndex  The loop index.
     * @return {@code this} instance.
     * @since 2.3
     */
    public StrBuilder appendSeparator(final String separator, final int loopIndex) {
        if (separator != null && loopIndex > 0) {
            append(separator);
        }
        return this;
    }

    /**
     * Appends one of both separators to the StrBuilder.
     * If the builder is currently empty it will append the defaultIfEmpty-separator
     * Otherwise it will append the standard-separator
     * <p>
     * Appending a null separator will have no effect.
     * The separator is appended using {@link #append(String)}.
     * </p>
     * <p>
     * This method is for example useful for constructing queries
     * </p>
     * <pre>
     * StrBuilder whereClause = new StrBuilder();
     * if (searchCommand.getPriority() != null) {
     *  whereClause.appendSeparator(" and", " where");
     *  whereClause.append(" priority = ?")
     * }
     * if (searchCommand.getComponent() != null) {
     *  whereClause.appendSeparator(" and", " where");
     *  whereClause.append(" component = ?")
     * }
     * selectClause.append(whereClause)
     * </pre>
     *
     * @param standard The separator if builder is not empty, null means no separator.
     * @param defaultIfEmpty The separator if builder is empty, null means no separator.
     * @return {@code this} instance.
     * @since 2.5
     */
    public StrBuilder appendSeparator(final String standard, final String defaultIfEmpty) {
        final String str = isEmpty() ? defaultIfEmpty : standard;
        if (str != null) {
            append(str);
        }
        return this;
    }

    /**
     * Appends current contents of this {@link StrBuilder} to the
     * provided {@link Appendable}.
     * <p>
     * This method tries to avoid doing any extra copies of contents.
     * </p>
     *
     * @param appendable  The appendable to append data to
     * @throws IOException Thrown if an I/O error occurs.
     * @since 3.4
     * @see #readFrom(Readable)
     */
    public void appendTo(final Appendable appendable) throws IOException {
        if (appendable instanceof Writer) {
            ((Writer) appendable).write(buffer, 0, size);
        } else if (appendable instanceof StringBuilder) {
            ((StringBuilder) appendable).append(buffer, 0, size);
        } else if (appendable instanceof StringBuffer) {
            ((StringBuffer) appendable).append(buffer, 0, size);
        } else if (appendable instanceof CharBuffer) {
            ((CharBuffer) appendable).put(buffer, 0, size);
        } else {
            appendable.append(this);
        }
    }

    /**
     * Appends an iterable placing separators between each value, but
     * not before the first or after the last.
     * Appending a null iterable will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param iterable  The iterable to append.
     * @param separator  The separator to use, null means no separator.
     * @return {@code this} instance.
     */
    public StrBuilder appendWithSeparators(final Iterable<?> iterable, final String separator) {
        if (iterable != null) {
            final String sep = Objects.toString(separator, StringUtils.EMPTY);
            final Iterator<?> it = iterable.iterator();
            while (it.hasNext()) {
                append(it.next());
                if (it.hasNext()) {
                    append(sep);
                }
            }
        }
        return this;
    }

    /**
     * Appends an iterator placing separators between each value, but
     * not before the first or after the last.
     * Appending a null iterator will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param it  The iterator to append.
     * @param separator  The separator to use, null means no separator.
     * @return {@code this} instance.
     */
    public StrBuilder appendWithSeparators(final Iterator<?> it, final String separator) {
        if (it != null) {
            final String sep = Objects.toString(separator, StringUtils.EMPTY);
            while (it.hasNext()) {
                append(it.next());
                if (it.hasNext()) {
                    append(sep);
                }
            }
        }
        return this;
    }

    /**
     * Appends an array placing separators between each value, but
     * not before the first or after the last.
     * Appending a null array will have no effect.
     * Each object is appended using {@link #append(Object)}.
     *
     * @param array  The array to append.
     * @param separator  The separator to use, null means no separator.
     * @return {@code this} instance.
     */
    public StrBuilder appendWithSeparators(final Object[] array, final String separator) {
        if (array != null && array.length > 0) {
            final String sep = Objects.toString(separator, StringUtils.EMPTY);
            append(array[0]);
            for (int i = 1; i < array.length; i++) {
                append(sep);
                append(array[i]);
            }
        }
        return this;
    }

    /**
     * Gets the contents of this builder as a Reader.
     * <p>
     * This method allows the contents of the builder to be read
     * using any standard method that expects a Reader.
     * </p>
     * <p>
     * To use, simply create a {@link StrBuilder}, populate it with
     * data, call {@code asReader}, and then read away.
     * </p>
     * <p>
     * The internal character array is shared between the builder and the reader.
     * This allows you to append to the builder after creating the reader,
     * and the changes will be picked up.
     * Note however, that no synchronization occurs, so you must perform
     * all operations with the builder and the reader in one thread.
     * </p>
     * <p>
     * The returned reader supports marking, and ignores the flush method.
     * </p>
     *
     * @return A reader that reads from this builder.
     */
    public Reader asReader() {
        return new StrBuilderReader();
    }

    /**
     * Creates a tokenizer that can tokenize the contents of this builder.
     * <p>
     * This method allows the contents of this builder to be tokenized.
     * The tokenizer will be setup by default to tokenize on space, tab,
     * newline and formfeed (as per StringTokenizer). These values can be
     * changed on the tokenizer class, before retrieving the tokens.
     * </p>
     * <p>
     * The returned tokenizer is linked to this builder. You may intermix
     * calls to the builder and tokenizer within certain limits, however
     * there is no synchronization. Once the tokenizer has been used once,
     * it must be {@link StrTokenizer#reset() reset} to pickup the latest
     * changes in the builder. For example:
     * </p>
     * <pre>
     * StrBuilder b = new StrBuilder();
     * b.append("a b ");
     * StrTokenizer t = b.asTokenizer();
     * String[] tokens1 = t.getTokenArray();  // returns a,b
     * b.append("c d ");
     * String[] tokens2 = t.getTokenArray();  // returns a,b (c and d ignored)
     * t.reset();              // reset causes builder changes to be picked up
     * String[] tokens3 = t.getTokenArray();  // returns a,b,c,d
     * </pre>
     * <p>
     * In addition to simply intermixing appends and tokenization, you can also
     * call the set methods on the tokenizer to alter how it tokenizes. Just
     * remember to call reset when you want to pickup builder changes.
     * </p>
     * <p>
     * Calling {@link StrTokenizer#reset(String)} or {@link StrTokenizer#reset(char[])}
     * with a non-null value will break the link with the builder.
     * </p>
     *
     * @return A tokenizer that is linked to this builder.
     */
    public StrTokenizer asTokenizer() {
        return new StrBuilderTokenizer();
    }

    /**
     * Gets this builder as a Writer that can be written to.
     * <p>
     * This method allows you to populate the contents of the builder
     * using any standard method that takes a Writer.
     * </p>
     * <p>
     * To use, simply create a {@link StrBuilder},
     * call {@code asWriter}, and populate away. The data is available
     * at any time using the methods of the {@link StrBuilder}.
     * </p>
     * <p>
     * The internal character array is shared between the builder and the writer.
     * This allows you to intermix calls that append to the builder and
     * write using the writer and the changes will be occur correctly.
     * Note however, that no synchronization occurs, so you must perform
     * all operations with the builder and the writer in one thread.
     * </p>
     * <p>
     * The returned writer ignores the close and flush methods.
     * </p>
     *
     * @return A writer that populates this builder
     */
    public Writer asWriter() {
        return new StrBuilderWriter();
    }

    /**
     * Implement the {@link Builder} interface.
     *
     * @return The builder as a String
     * @since 3.2
     * @see #toString()
     */
    @Override
    public String build() {
        return toString();
    }

    /**
     * Gets the current size of the internal character array buffer.
     *
     * @return The capacity.
     */
    public int capacity() {
        return buffer.length;
    }

    /**
     * Gets the character at the specified index.
     *
     * @param index  The index to retrieve, must be valid.
     * @return The character at the index.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     * @see #setCharAt(int, char)
     * @see #deleteCharAt(int)
     */
    @Override
    public char charAt(final int index) {
        if (index < 0 || index >= length()) {
            throw new StringIndexOutOfBoundsException(index);
        }
        return buffer[index];
    }

    /**
     * Clears the string builder (convenience Collections API style method).
     * <p>
     * This method does not reduce the size of the internal character buffer.
     * To do that, call {@code clear()} followed by {@link #minimizeCapacity()}.
     * </p>
     *
     * @return {@code this} instance.
     */
    public StrBuilder clear() {
        size = 0;
        ArrayFill.clear(buffer);
        return this;
    }

    /**
     * Checks if the string builder contains the specified char.
     *
     * @param ch  The character to find.
     * @return true if the builder contains the character.
     */
    public boolean contains(final char ch) {
        final char[] thisBuf = buffer;
        for (int i = 0; i < this.size; i++) {
            if (thisBuf[i] == ch) {
                return true;
            }
        }
        return false;
    }

    /**
     * Checks if the string builder contains the specified string.
     *
     * @param str  The string to find.
     * @return true if the builder contains the string.
     */
    public boolean contains(final String str) {
        return indexOf(str, 0) >= 0;
    }

    /**
     * Checks if the string builder contains a string matched using the
     * specified matcher.
     * <p>
     * Matchers can be used to perform advanced searching behavior.
     * For example you could write a matcher to search for the character
     * 'a' followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use, null returns -1.
     * @return true if the matcher finds a match in the builder.
     */
    public boolean contains(final StrMatcher matcher) {
        return indexOf(matcher, 0) >= 0;
    }

    /**
     * Deletes the characters between the two specified indices.
     *
     * @param startIndex The start index, inclusive, must be valid.
     * @param endIndex   The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder delete(final int startIndex, int endIndex) {
        endIndex = validateRange(startIndex, endIndex);
        final int len = endIndex - startIndex;
        if (len > 0) {
            deleteImpl(startIndex, endIndex, len);
        }
        return this;
    }

    /**
     * Deletes the character wherever it occurs in the builder.
     *
     * @param ch  The character to delete.
     * @return {@code this} instance.
     */
    public StrBuilder deleteAll(final char ch) {
        for (int i = 0; i < size; i++) {
            if (buffer[i] == ch) {
                final int start = i;
                while (++i < size) {
                    if (buffer[i] != ch) {
                        break;
                    }
                }
                final int len = i - start;
                deleteImpl(start, i, len);
                i -= len;
            }
        }
        return this;
    }

    /**
     * Deletes the string wherever it occurs in the builder.
     *
     * @param str  The string to delete, null causes no action.
     * @return {@code this} instance.
     */
    public StrBuilder deleteAll(final String str) {
        final int len = StringUtils.length(str);
        if (len > 0) {
            int index = indexOf(str, 0);
            while (index >= 0) {
                deleteImpl(index, index + len, len);
                index = indexOf(str, index);
            }
        }
        return this;
    }

    /**
     * Deletes all parts of the builder that the matcher matches.
     * <p>
     * Matchers can be used to perform advanced deletion behavior.
     * For example you could write a matcher to delete all occurrences
     * where the character 'a' is followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use to find the deletion, null causes no action.
     * @return {@code this} instance.
     */
    public StrBuilder deleteAll(final StrMatcher matcher) {
        return replace(matcher, null, 0, size, -1);
    }

    /**
     * Deletes the character at the specified index.
     *
     * @param index  The index to delete.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     * @see #charAt(int)
     * @see #setCharAt(int, char)
     */
    public StrBuilder deleteCharAt(final int index) {
        if (index < 0 || index >= size) {
            throw new StringIndexOutOfBoundsException(index);
        }
        deleteImpl(index, index + 1, 1);
        return this;
    }

    /**
     * Deletes the character wherever it occurs in the builder.
     *
     * @param ch  The character to delete.
     * @return {@code this} instance.
     */
    public StrBuilder deleteFirst(final char ch) {
        for (int i = 0; i < size; i++) {
            if (buffer[i] == ch) {
                deleteImpl(i, i + 1, 1);
                break;
            }
        }
        return this;
    }

    /**
     * Deletes the string wherever it occurs in the builder.
     *
     * @param str  The string to delete, null causes no action.
     * @return {@code this} instance.
     */
    public StrBuilder deleteFirst(final String str) {
        final int len = StringUtils.length(str);
        if (len > 0) {
            final int index = indexOf(str, 0);
            if (index >= 0) {
                deleteImpl(index, index + len, len);
            }
        }
        return this;
    }

    /**
     * Deletes the first match within the builder using the specified matcher.
     * <p>
     * Matchers can be used to perform advanced deletion behavior.
     * For example you could write a matcher to delete
     * where the character 'a' is followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use to find the deletion, null causes no action.
     * @return {@code this} instance.
     */
    public StrBuilder deleteFirst(final StrMatcher matcher) {
        return replace(matcher, null, 0, size, 1);
    }

    /**
     * Internal method to delete a range without validation.
     *
     * @param startIndex  The start index, must be valid.
     * @param endIndex  The end index (exclusive), must be valid.
     * @param len  The length, must be valid.
     * @throws IndexOutOfBoundsException Thrown if any index is invalid.
     */
    private void deleteImpl(final int startIndex, final int endIndex, final int len) {
        System.arraycopy(buffer, endIndex, buffer, startIndex, size - endIndex);
        size -= len;
        ArrayFill.clear(buffer, size, size + len);
    }

    /**
     * Checks whether this builder ends with the specified string.
     * <p>
     * Note that this method handles null input quietly, unlike String.
     * </p>
     *
     * @param str  The string to search for, null returns false.
     * @return true if the builder ends with the string.
     */
    public boolean endsWith(final String str) {
        if (str == null) {
            return false;
        }
        final int len = str.length();
        if (len == 0) {
            return true;
        }
        if (len > size) {
            return false;
        }
        int pos = size - len;
        for (int i = 0; i < len; i++, pos++) {
            if (buffer[pos] != str.charAt(i)) {
                return false;
            }
        }
        return true;
    }

    /**
     * Checks the capacity and ensures that it is at least the size specified.
     *
     * @param capacity  The capacity to ensure.
     * @return {@code this} instance.
     */
    public StrBuilder ensureCapacity(final int capacity) {
        if (capacity > buffer.length) {
            buffer = ArrayUtils.arraycopy(buffer, 0, 0, size, () -> new char[capacity * 2]);
        }
        return this;
    }

    /**
     * Checks the contents of this builder against another to see if they
     * contain the same character content.
     *
     * @param obj  The object to check, null returns false.
     * @return true if the builders contain the same characters in the same order.
     */
    @Override
    public boolean equals(final Object obj) {
        return obj instanceof StrBuilder && equals((StrBuilder) obj);
    }

    /**
     * Checks the contents of this builder against another to see if they
     * contain the same character content.
     *
     * @param other  The object to check, null returns false.
     * @return true if the builders contain the same characters in the same order.
     */
    public boolean equals(final StrBuilder other) {
        if (this == other) {
            return true;
        }
        if (other == null || this.size != other.size) {
            return false;
        }
        final char[] thisBuf = this.buffer;
        final char[] otherBuf = other.buffer;
        for (int i = size - 1; i >= 0; i--) {
            if (thisBuf[i] != otherBuf[i]) {
                return false;
            }
        }
        return true;
    }

    /**
     * Checks the contents of this builder against another to see if they
     * contain the same character content ignoring case.
     *
     * @param other  The object to check, null returns false.
     * @return true if the builders contain the same characters in the same order.
     */
    public boolean equalsIgnoreCase(final StrBuilder other) {
        if (this == other) {
            return true;
        }
        if (this.size != other.size) {
            return false;
        }
        final char[] thisBuf = this.buffer;
        final char[] otherBuf = other.buffer;
        for (int i = size - 1; i >= 0; i--) {
            final char c1 = thisBuf[i];
            final char c2 = otherBuf[i];
            if (c1 != c2) {
                final char u1 = Character.toUpperCase(c1);
                final char u2 = Character.toUpperCase(c2);
                if (u1 != u2 && Character.toLowerCase(u1) != Character.toLowerCase(u2)) {
                    return false;
                }
            }
        }
        return true;
    }

    /**
     * Gets the internal buffer for testing.
     *
     * @return The internal buffer.
     */
    char[] getBuffer() {
        return buffer;
    }

    /**
     * Gets the characters by copying them into the specified array.
     *
     * @param destination  The destination array, null will cause an array to be created.
     * @return The input array, unless that was null or too small.
     */
    public char[] getChars(char[] destination) {
        final int len = length();
        if (destination == null || destination.length < len) {
            destination = new char[len];
        }
        return ArrayUtils.arraycopy(buffer, 0, destination, 0, len);
    }

    /**
     * Gets the characters by copying them into the specified array.
     *
     * @param startIndex  first index to copy, inclusive, must be valid.
     * @param endIndex  last index, exclusive, must be valid.
     * @param destination  The destination array, must not be null or too small.
     * @param destinationIndex  The index to start copying in destination.
     * @throws NullPointerException Thrown if the array is null.
     * @throws IndexOutOfBoundsException Thrown if any index is invalid.
     */
    public void getChars(final int startIndex, final int endIndex, final char[] destination, final int destinationIndex) {
        if (startIndex < 0) {
            throw new StringIndexOutOfBoundsException(startIndex);
        }
        if (endIndex < 0 || endIndex > length()) {
            throw new StringIndexOutOfBoundsException(endIndex);
        }
        if (startIndex > endIndex) {
            throw new StringIndexOutOfBoundsException("end < start");
        }
        System.arraycopy(buffer, startIndex, destination, destinationIndex, endIndex - startIndex);
    }

    /**
     * Gets the text to be appended when a {@link #appendNewLine() new line} is added.
     *
     * @return The new line text, {@code null} means use the system default from {@link System#lineSeparator()}.
     */
    public String getNewLineText() {
        return newLine;
    }

    /**
     * Gets the text to be appended when null is added.
     *
     * @return The null text, null means no append.
     */
    public String getNullText() {
        return nullText;
    }

    /**
     * Gets a suitable hash code for this builder.
     *
     * @return A hash code.
     */
    @Override
    public int hashCode() {
        final char[] buf = buffer;
        int hash = 0;
        for (int i = size - 1; i >= 0; i--) {
            hash = 31 * hash + buf[i];
        }
        return hash;
    }

    /**
     * Searches the string builder to find the first reference to the specified char.
     *
     * @param ch  The character to find.
     * @return The first index of the character, or -1 if not found.
     */
    public int indexOf(final char ch) {
        return indexOf(ch, 0);
    }

    /**
     * Searches the string builder to find the first reference to the specified char.
     *
     * @param ch  The character to find.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The first index of the character, or -1 if not found.
     */
    public int indexOf(final char ch, int startIndex) {
        startIndex = Math.max(startIndex, 0);
        if (startIndex >= size) {
            return -1;
        }
        final char[] thisBuf = buffer;
        for (int i = startIndex; i < size; i++) {
            if (thisBuf[i] == ch) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Searches the string builder to find the first reference to the specified string.
     * <p>
     * Note that a null input string will return -1, whereas the JDK throws an exception.
     * </p>
     *
     * @param str  The string to find, null returns -1.
     * @return The first index of the string, or -1 if not found.
     */
    public int indexOf(final String str) {
        return indexOf(str, 0);
    }

    /**
     * Searches the string builder to find the first reference to the specified
     * string starting searching from the given index.
     * <p>
     * Note that a null input string will return -1, whereas the JDK throws an exception.
     * </p>
     *
     * @param str  The string to find, null returns -1.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The first index of the string, or -1 if not found.
     */
    public int indexOf(final String str, final int startIndex) {
        return Strings.CS.indexOf(this, str, startIndex);
    }

    /**
     * Searches the string builder using the matcher to find the first match.
     * <p>
     * Matchers can be used to perform advanced searching behavior.
     * For example you could write a matcher to find the character 'a'
     * followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use, null returns -1.
     * @return The first index matched, or -1 if not found.
     */
    public int indexOf(final StrMatcher matcher) {
        return indexOf(matcher, 0);
    }

    /**
     * Searches the string builder using the matcher to find the first
     * match searching from the given index.
     * <p>
     * Matchers can be used to perform advanced searching behavior.
     * For example you could write a matcher to find the character 'a'
     * followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use, null returns -1.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The first index matched, or -1 if not found.
     */
    public int indexOf(final StrMatcher matcher, int startIndex) {
        startIndex = Math.max(startIndex, 0);
        if (matcher == null || startIndex >= size) {
            return -1;
        }
        final int len = size;
        final char[] buf = buffer;
        for (int i = startIndex; i < len; i++) {
            if (matcher.isMatch(buf, i, startIndex, len) > 0) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(int index, final boolean value) {
        validateIndex(index);
        if (value) {
            ensureCapacity(size + 4);
            System.arraycopy(buffer, index, buffer, index + 4, size - index);
            buffer[index++] = 't';
            buffer[index++] = 'r';
            buffer[index++] = 'u';
            buffer[index] = 'e';
            size += 4;
        } else {
            ensureCapacity(size + 5);
            System.arraycopy(buffer, index, buffer, index + 5, size - index);
            buffer[index++] = 'f';
            buffer[index++] = 'a';
            buffer[index++] = 'l';
            buffer[index++] = 's';
            buffer[index] = 'e';
            size += 5;
        }
        return this;
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final char value) {
        validateIndex(index);
        ensureCapacity(size + 1);
        System.arraycopy(buffer, index, buffer, index + 1, size - index);
        buffer[index] = value;
        size++;
        return this;
    }

    /**
     * Inserts the character array into this builder.
     * Inserting null will use the stored null text value.
     *
     * @param index  The index to add at, must be valid.
     * @param chars  The char array to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final char[] chars) {
        validateIndex(index);
        if (chars == null) {
            return insert(index, nullText);
        }
        final int len = chars.length;
        if (len > 0) {
            ensureCapacity(size + len);
            System.arraycopy(buffer, index, buffer, index + len, size - index);
            System.arraycopy(chars, 0, buffer, index, len);
            size += len;
        }
        return this;
    }

    /**
     * Inserts part of the character array into this builder.
     * Inserting null will use the stored null text value.
     *
     * @param index  The index to add at, must be valid.
     * @param chars  The char array to insert.
     * @param offset  The offset into the character array to start at, must be valid.
     * @param length  The length of the character array part to copy, must be positive.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if any index is invalid.
     */
    public StrBuilder insert(final int index, final char[] chars, final int offset, final int length) {
        validateIndex(index);
        if (chars == null) {
            return insert(index, nullText);
        }
        if (offset < 0 || offset > chars.length) {
            throw new StringIndexOutOfBoundsException("Invalid offset: " + offset);
        }
        if (length < 0 || offset + length > chars.length) {
            throw new StringIndexOutOfBoundsException("Invalid length: " + length);
        }
        if (length > 0) {
            ensureCapacity(size + length);
            System.arraycopy(buffer, index, buffer, index + length, size - index);
            System.arraycopy(chars, offset, buffer, index, length);
            size += length;
        }
        return this;
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final double value) {
        return insert(index, String.valueOf(value));
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final float value) {
        return insert(index, String.valueOf(value));
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final int value) {
        return insert(index, String.valueOf(value));
    }

    /**
     * Inserts the value into this builder.
     *
     * @param index  The index to add at, must be valid.
     * @param value  The value to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final long value) {
        return insert(index, String.valueOf(value));
    }

    /**
     * Inserts the string representation of an object into this builder.
     * Inserting null will use the stored null text value.
     *
     * @param index  The index to add at, must be valid.
     * @param obj  The object to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, final Object obj) {
        if (obj == null) {
            return insert(index, nullText);
        }
        return insert(index, obj.toString());
    }

    /**
     * Inserts the string into this builder.
     * Inserting null will use the stored null text value.
     *
     * @param index  The index to add at, must be valid.
     * @param str  The string to insert.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder insert(final int index, String str) {
        validateIndex(index);
        if (str == null) {
            str = nullText;
        }
        if (str != null) {
            final int strLen = str.length();
            if (strLen > 0) {
                final int newSize = size + strLen;
                ensureCapacity(newSize);
                System.arraycopy(buffer, index, buffer, index + strLen, size - index);
                size = newSize;
                str.getChars(0, strLen, buffer, index);
            }
        }
        return this;
    }

    /**
     * Tests whether the string builder is empty (convenience Collections API style method).
     * <p>
     * This method is the same as checking {@link #length()} and is provided to match the
     * API of Collections.
     * </p>
     *
     * @return {@code true} if the size is {@code 0}.
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * Tests whether the string builder is not empty (convenience Collections API style method).
     * <p>
     * This method is the same as checking {@link #length()} and is provided to match the
     * API of Collections.
     * </p>
     *
     * @return {@code true} if the size is greater than {@code 0}.
     * @since 3.12.0
     */
    public boolean isNotEmpty() {
        return size > 0;
    }

    /**
     * Searches the string builder to find the last reference to the specified char.
     *
     * @param ch  The character to find.
     * @return The last index of the character, or -1 if not found.
     */
    public int lastIndexOf(final char ch) {
        return lastIndexOf(ch, size - 1);
    }

    /**
     * Searches the string builder to find the last reference to the specified char.
     *
     * @param ch  The character to find.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The last index of the character, or -1 if not found.
     */
    public int lastIndexOf(final char ch, int startIndex) {
        startIndex = startIndex >= size ? size - 1 : startIndex;
        if (startIndex < 0) {
            return -1;
        }
        for (int i = startIndex; i >= 0; i--) {
            if (buffer[i] == ch) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Searches the string builder to find the last reference to the specified string.
     * <p>
     * Note that a null input string will return -1, whereas the JDK throws an exception.
     * </p>
     *
     * @param str  The string to find, null returns -1.
     * @return The last index of the string, or -1 if not found.
     */
    public int lastIndexOf(final String str) {
        return lastIndexOf(str, size);
    }

    /**
     * Searches the string builder to find the last reference to the specified
     * string starting searching from the given index.
     * <p>
     * Note that a null input string will return -1, whereas the JDK throws an exception.
     * </p>
     *
     * @param str  The string to find, null returns -1.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The last index of the string, or -1 if not found.
     */
    public int lastIndexOf(final String str, final int startIndex) {
        return Strings.CS.lastIndexOf(this, str, startIndex);
    }

    /**
     * Searches the string builder using the matcher to find the last match.
     * <p>
     * Matchers can be used to perform advanced searching behavior.
     * For example you could write a matcher to find the character 'a'
     * followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use, null returns -1.
     * @return The last index matched, or -1 if not found.
     */
    public int lastIndexOf(final StrMatcher matcher) {
        return lastIndexOf(matcher, size);
    }

    /**
     * Searches the string builder using the matcher to find the last
     * match searching from the given index.
     * <p>
     * Matchers can be used to perform advanced searching behavior.
     * For example you could write a matcher to find the character 'a'
     * followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use, null returns -1.
     * @param startIndex  The index to start at, invalid index rounded to edge.
     * @return The last index matched, or -1 if not found.
     */
    public int lastIndexOf(final StrMatcher matcher, int startIndex) {
        startIndex = startIndex >= size ? size - 1 : startIndex;
        if (matcher == null || startIndex < 0) {
            return -1;
        }
        final char[] buf = buffer;
        final int endIndex = startIndex + 1;
        for (int i = startIndex; i >= 0; i--) {
            if (matcher.isMatch(buf, i, 0, endIndex) > 0) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Extracts the leftmost characters from the string builder without
     * throwing an exception.
     * <p>
     * This method extracts the left {@code length} characters from
     * the builder. If this many characters are not available, the whole
     * builder is returned. Thus the returned string may be shorter than the
     * length requested.
     * </p>
     *
     * @param length  The number of characters to extract, negative returns empty string.
     * @return The new string.
     */
    public String leftString(final int length) {
        if (length <= 0) {
            return StringUtils.EMPTY;
        }
        if (length >= size) {
            return new String(buffer, 0, size);
        }
        return new String(buffer, 0, length);
    }

    /**
     * Gets the length of the string builder.
     *
     * @return The length
     */
    @Override
    public int length() {
        return size;
    }

    /**
     * Extracts some characters from the middle of the string builder without
     * throwing an exception.
     * <p>
     * This method extracts {@code length} characters from the builder
     * at the specified index.
     * If the index is negative it is treated as zero.
     * If the index is greater than the builder size, it is treated as the builder size.
     * If the length is negative, the empty string is returned.
     * If insufficient characters are available in the builder, as much as possible is returned.
     * Thus the returned string may be shorter than the length requested.
     * </p>
     *
     * @param index  The index to start at, negative means zero.
     * @param length  The number of characters to extract, negative returns empty string.
     * @return The new string.
     */
    public String midString(int index, final int length) {
        if (index < 0) {
            index = 0;
        }
        if (length <= 0 || index >= size) {
            return StringUtils.EMPTY;
        }
        if (size - index <= length) {
            return new String(buffer, index, size - index);
        }
        return new String(buffer, index, length);
    }

    /**
     * Minimizes the capacity to the actual length of the string.
     *
     * @return {@code this} instance.
     */
    public StrBuilder minimizeCapacity() {
        if (buffer.length > length()) {
            buffer = ArrayUtils.arraycopy(buffer, 0, 0, size, () -> new char[length()]);
        }
        return this;
    }

    /**
     * If possible, reads chars from the provided {@link Readable} directly into underlying
     * character buffer without making extra copies.
     *
     * @param readable  object to read from.
     * @return The number of characters read.
     * @throws IOException Thrown if an I/O error occurs.
     * @since 3.4
     * @see #appendTo(Appendable)
     */
    public int readFrom(final Readable readable) throws IOException {
        final int oldSize = size;
        if (readable instanceof Reader) {
            final Reader r = (Reader) readable;
            ensureCapacity(size + 1);
            int read;
            while ((read = r.read(buffer, size, buffer.length - size)) != -1) {
                size += read;
                ensureCapacity(size + 1);
            }
        } else if (readable instanceof CharBuffer) {
            final CharBuffer cb = (CharBuffer) readable;
            final int remaining = cb.remaining();
            ensureCapacity(size + remaining);
            cb.get(buffer, size, remaining);
            size += remaining;
        } else {
            while (true) {
                ensureCapacity(size + 1);
                final CharBuffer buf = CharBuffer.wrap(buffer, size, buffer.length - size);
                final int read = readable.read(buf);
                if (read == -1) {
                    break;
                }
                size += read;
            }
        }
        return size - oldSize;
    }

    /**
     * Replaces a portion of the string builder with another string. The length of the inserted string does not have to match the removed length.
     *
     * @param startIndex The start index, inclusive, must be valid.
     * @param endIndex   The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @param replaceStr The string to replace with, null means delete range.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public StrBuilder replace(final int startIndex, int endIndex, final String replaceStr) {
        endIndex = validateRange(startIndex, endIndex);
        final int insertLen = StringUtils.length(replaceStr);
        replaceImpl(startIndex, endIndex, endIndex - startIndex, replaceStr, insertLen);
        return this;
    }

    /**
     * Advanced search and replaces within the builder using a matcher.
     * <p>
     * Matchers can be used to perform advanced behavior. For example you could write a matcher to delete all occurrences where the character 'a' is followed by
     * a number.
     * </p>
     *
     * @param matcher      The matcher to use to find the deletion, null causes no action.
     * @param replaceStr   The string to replace the match with, null is a delete.
     * @param startIndex   The start index, inclusive, must be valid.
     * @param endIndex     The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @param replaceCount The number of times to replace, -1 for replace all.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if start index is invalid.
     */
    public StrBuilder replace(final StrMatcher matcher, final String replaceStr, final int startIndex, int endIndex, final int replaceCount) {
        endIndex = validateRange(startIndex, endIndex);
        return replaceImpl(matcher, replaceStr, startIndex, endIndex, replaceCount);
    }

    /**
     * Replaces the search character with the replace character
     * throughout the builder.
     *
     * @param search  The search character.
     * @param replace  The replace character.
     * @return {@code this} instance.
     */
    public StrBuilder replaceAll(final char search, final char replace) {
        if (search != replace) {
            for (int i = 0; i < size; i++) {
                if (buffer[i] == search) {
                    buffer[i] = replace;
                }
            }
        }
        return this;
    }

    /**
     * Replaces the search string with the replace string throughout the builder.
     *
     * @param searchStr  The search string, null causes no action to occur.
     * @param replaceStr  The replace string, null is equivalent to an empty string.
     * @return {@code this} instance.
     */
    public StrBuilder replaceAll(final String searchStr, final String replaceStr) {
        final int searchLen = StringUtils.length(searchStr);
        if (searchLen > 0) {
            final int replaceLen = StringUtils.length(replaceStr);
            int index = indexOf(searchStr, 0);
            while (index >= 0) {
                replaceImpl(index, index + searchLen, searchLen, replaceStr, replaceLen);
                index = indexOf(searchStr, index + replaceLen);
            }
        }
        return this;
    }

    /**
     * Replaces all matches within the builder with the replace string.
     * <p>
     * Matchers can be used to perform advanced replace behavior.
     * For example you could write a matcher to replace all occurrences
     * where the character 'a' is followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use to find the deletion, null causes no action.
     * @param replaceStr  The replace string, null is equivalent to an empty string.
     * @return {@code this} instance.
     */
    public StrBuilder replaceAll(final StrMatcher matcher, final String replaceStr) {
        return replace(matcher, replaceStr, 0, size, -1);
    }

    /**
     * Replaces the first instance of the search character with the
     * replace character in the builder.
     *
     * @param search  The search character.
     * @param replace  The replace character.
     * @return {@code this} instance.
     */
    public StrBuilder replaceFirst(final char search, final char replace) {
        if (search != replace) {
            for (int i = 0; i < size; i++) {
                if (buffer[i] == search) {
                    buffer[i] = replace;
                    break;
                }
            }
        }
        return this;
    }

    /**
     * Replaces the first instance of the search string with the replace string.
     *
     * @param searchStr  The search string, null causes no action to occur.
     * @param replaceStr  The replace string, null is equivalent to an empty string.
     * @return {@code this} instance.
     */
    public StrBuilder replaceFirst(final String searchStr, final String replaceStr) {
        final int searchLen = StringUtils.length(searchStr);
        if (searchLen > 0) {
            final int index = indexOf(searchStr, 0);
            if (index >= 0) {
                final int replaceLen = StringUtils.length(replaceStr);
                replaceImpl(index, index + searchLen, searchLen, replaceStr, replaceLen);
            }
        }
        return this;
    }

    /**
     * Replaces the first match within the builder with the replace string.
     * <p>
     * Matchers can be used to perform advanced replace behavior.
     * For example you could write a matcher to replace
     * where the character 'a' is followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use to find the deletion, null causes no action.
     * @param replaceStr  The replace string, null is equivalent to an empty string.
     * @return {@code this} instance.
     */
    public StrBuilder replaceFirst(final StrMatcher matcher, final String replaceStr) {
        return replace(matcher, replaceStr, 0, size, 1);
    }

    /**
     * Internal method to replace a range without validation.
     *
     * @param startIndex  The start index (inclusive), must be valid.
     * @param endIndex  The end index (exclusive), must be valid.
     * @param removeLen  The length to remove (endIndex - startIndex), must be valid.
     * @param insertStr  The string to replace with, null means delete range.
     * @param insertLen  The length of the insert string, must be valid.
     * @throws IndexOutOfBoundsException Thrown if any index is invalid.
     */
    private void replaceImpl(final int startIndex, final int endIndex, final int removeLen, final String insertStr, final int insertLen) {
        final int newSize = size - removeLen + insertLen;
        if (insertLen != removeLen) {
            ensureCapacity(newSize);
            System.arraycopy(buffer, endIndex, buffer, startIndex + insertLen, size - endIndex);
            if (size > newSize) {
                ArrayFill.clear(buffer, newSize, size);
            }
            size = newSize;
        }
        if (insertLen > 0) {
            insertStr.getChars(0, insertLen, buffer, startIndex);
        }
    }

    /**
     * Replaces within the builder using a matcher.
     * <p>
     * Matchers can be used to perform advanced behavior.
     * For example you could write a matcher to delete all occurrences
     * where the character 'a' is followed by a number.
     * </p>
     *
     * @param matcher  The matcher to use to find the deletion, null causes no action.
     * @param replaceStr  The string to replace the match with, null is a delete.
     * @param from  The start index, must be valid.
     * @param to  The end index (exclusive), must be valid.
     * @param replaceCount  The number of times to replace, -1 for replace all.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if any index is invalid.
     */
    private StrBuilder replaceImpl(
            final StrMatcher matcher, final String replaceStr,
            final int from, int to, int replaceCount) {
        if (matcher == null || size == 0) {
            return this;
        }
        final int replaceLen = StringUtils.length(replaceStr);
        for (int i = from; i < to && replaceCount != 0; i++) {
            final char[] buf = buffer;
            final int removeLen = matcher.isMatch(buf, i, from, to);
            if (removeLen > 0) {
                replaceImpl(i, i + removeLen, removeLen, replaceStr, replaceLen);
                to = to - removeLen + replaceLen;
                i = i + replaceLen - 1;
                if (replaceCount > 0) {
                    replaceCount--;
                }
            }
        }
        return this;
    }

    /**
     * Reverses the string builder placing each character in the opposite index.
     *
     * @return {@code this} instance.
     */
    public StrBuilder reverse() {
        if (size == 0) {
            return this;
        }

        final int half = size / 2;
        final char[] buf = buffer;
        boolean hasSurrogates = false;
        for (int leftIdx = 0, rightIdx = size - 1; leftIdx < half; leftIdx++, rightIdx--) {
            final char left = buf[leftIdx];
            final char right = buf[rightIdx];
            buf[leftIdx] = right;
            buf[rightIdx] = left;
            hasSurrogates |= Character.isSurrogate(left) || Character.isSurrogate(right);
        }
        if (hasSurrogates) {
            // The plain swap leaves each surrogate pair in low-high order; restore the high-low order so a
            // reversed supplementary code point stays a valid pair, matching StringBuilder#reverse().
            for (int i = 0; i < size - 1; i++) {
                if (Character.isLowSurrogate(buf[i]) && Character.isHighSurrogate(buf[i + 1])) {
                    final char low = buf[i];
                    buf[i] = buf[i + 1];
                    buf[i + 1] = low;
                    i++;
                }
            }
        }
        return this;
    }

    /**
     * Extracts the rightmost characters from the string builder without
     * throwing an exception.
     * <p>
     * This method extracts the right {@code length} characters from
     * the builder. If this many characters are not available, the whole
     * builder is returned. Thus the returned string may be shorter than the
     * length requested.
     * </p>
     *
     * @param length  The number of characters to extract, negative returns empty string.
     * @return The new string.
     */
    public String rightString(final int length) {
        if (length <= 0) {
            return StringUtils.EMPTY;
        }
        if (length >= size) {
            return new String(buffer, 0, size);
        }
        return new String(buffer, size - length, length);
    }

    /**
     * Sets the character at the specified index.
     *
     * @param index  The index to set.
     * @param ch  The new character.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     * @see #charAt(int)
     * @see #deleteCharAt(int)
     */
    public StrBuilder setCharAt(final int index, final char ch) {
        if (index < 0 || index >= length()) {
            throw new StringIndexOutOfBoundsException(index);
        }
        buffer[index] = ch;
        return this;
    }

    /**
     * Sets the length of the builder by removing trailing characters or adding Unicode zero characters.
     *
     * @param length  The length to set to, must be zero or positive.
     * @return {@code this} instance.
     * @throws IndexOutOfBoundsException Thrown if the length is negative.
     */
    public StrBuilder setLength(final int length) {
        if (length < 0) {
            throw new StringIndexOutOfBoundsException(length);
        }
        if (length < size) {
            ArrayFill.clear(buffer, length, size);
        } else if (length > size) {
            ensureCapacity(length);
            ArrayFill.clear(buffer, size, length);
        }
        size = length;
        return this;
    }

    /**
     * Sets the text to be appended when {@link #appendNewLine() new line} is called.
     *
     * @param newLine The new line text, {@code null} means use the system default from {@link System#lineSeparator()}.
     * @return {@code this} instance.
     */
    public StrBuilder setNewLineText(final String newLine) {
        this.newLine = newLine;
        return this;
    }

    /**
     * Sets the text to be appended when null is added.
     *
     * @param nullText  The null text, null means no append.
     * @return {@code this} instance.
     */
    public StrBuilder setNullText(String nullText) {
        if (StringUtils.isEmpty(nullText)) {
            nullText = null;
        }
        this.nullText = nullText;
        return this;
    }

    /**
     * Gets the length of the string builder.
     * <p>
     * This method is the same as {@link #length()} and is provided to match the
     * API of Collections.
     * </p>
     *
     * @return The length.
     */
    public int size() {
        return size;
    }

    /**
     * Checks whether this builder starts with the specified string.
     * <p>
     * Note that this method handles null input quietly, unlike String.
     * </p>
     *
     * @param str  The string to search for, null returns false.
     * @return true if the builder starts with the string.
     */
    public boolean startsWith(final String str) {
        if (str == null) {
            return false;
        }
        final int len = str.length();
        if (len == 0) {
            return true;
        }
        if (len > size) {
            return false;
        }
        for (int i = 0; i < len; i++) {
            if (buffer[i] != str.charAt(i)) {
                return false;
            }
        }
        return true;
    }

    /**
     * {@inheritDoc}
     *
     * @since 3.0
     */
    @Override
    public CharSequence subSequence(final int startIndex, final int endIndex) {
      if (startIndex < 0) {
          throw new StringIndexOutOfBoundsException(startIndex);
      }
      if (endIndex > size) {
          throw new StringIndexOutOfBoundsException(endIndex);
      }
      if (startIndex > endIndex) {
          throw new StringIndexOutOfBoundsException(endIndex - startIndex);
      }
      return substring(startIndex, endIndex);
    }

    /**
     * Extracts a portion of this string builder as a string.
     *
     * @param start  The start index, inclusive, must be valid.
     * @return The new string.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public String substring(final int start) {
        return substring(start, size);
    }

    /**
     * Extracts a portion of this string builder as a string.
     * <p>
     * Note: This method treats an endIndex greater than the length of the builder as equal to the length of the builder, and continues without error, unlike
     * StringBuffer or String.
     * </p>
     *
     * @param startIndex The start index, inclusive, must be valid.
     * @param endIndex   The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @return The new string.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    public String substring(final int startIndex, int endIndex) {
        endIndex = validateRange(startIndex, endIndex);
        return new String(buffer, startIndex, endIndex - startIndex);
    }

    /**
     * Copies the builder's character array into a new character array.
     *
     * @return A new array that represents the contents of the builder.
     */
    public char[] toCharArray() {
        if (size == 0) {
            return ArrayUtils.EMPTY_CHAR_ARRAY;
        }
        return ArrayUtils.arraycopy(buffer, 0, 0, size, char[]::new);
    }

    /**
     * Copies part of the builder's character array into a new character array.
     *
     * @param startIndex The start index, inclusive, must be valid.
     * @param endIndex   The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @return A new array that holds part of the contents of the builder.
     * @throws IndexOutOfBoundsException Thrown if startIndex is invalid, or if endIndex is invalid (but endIndex greater than size is valid).
     */
    public char[] toCharArray(final int startIndex, int endIndex) {
        endIndex = validateRange(startIndex, endIndex);
        final int len = endIndex - startIndex;
        if (len == 0) {
            return ArrayUtils.EMPTY_CHAR_ARRAY;
        }
        return ArrayUtils.arraycopy(buffer, startIndex, 0, len, char[]::new);
    }

    /**
     * Gets a String version of the string builder, creating a new instance
     * each time the method is called.
     * <p>
     * Note that unlike StringBuffer, the string version returned is
     * independent of the string builder.
     * </p>
     *
     * @return The builder as a String.
     */
    @Override
    public String toString() {
        return new String(buffer, 0, size);
    }

    /**
     * Gets a StringBuffer version of the string builder, creating a
     * new instance each time the method is called.
     *
     * @return The builder as a StringBuffer.
     */
    public StringBuffer toStringBuffer() {
        return new StringBuffer(size).append(buffer, 0, size);
    }

    /**
     * Gets a StringBuilder version of the string builder, creating a
     * new instance each time the method is called.
     *
     * @return The builder as a StringBuilder.
     * @since 3.2
     */
    public StringBuilder toStringBuilder() {
        return new StringBuilder(size).append(buffer, 0, size);
    }

    /**
     * Trims the builder by removing characters less than or equal to a space
     * from the beginning and end.
     *
     * @return {@code this} instance.
     */
    public StrBuilder trim() {
        if (size == 0) {
            return this;
        }
        int len = size;
        final char[] buf = buffer;
        int pos = 0;
        while (pos < len && buf[pos] <= ' ') {
            pos++;
        }
        while (pos < len && buf[len - 1] <= ' ') {
            len--;
        }
        if (len < size) {
            delete(len, size);
        }
        if (pos > 0) {
            delete(0, pos);
        }
        return this;
    }

    /**
     * Validates parameters defining a single index in the builder.
     *
     * @param index  The index, must be valid.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    protected void validateIndex(final int index) {
        if (index < 0 || index > size) {
            throw new StringIndexOutOfBoundsException(index);
        }
    }

    /**
     * Validates parameters defining a range of the builder.
     *
     * @param startIndex The start index, inclusive, must be valid.
     * @param endIndex   The end index, exclusive, must be valid except that if too large it is treated as end of string.
     * @return The new string.
     * @throws IndexOutOfBoundsException Thrown if the index is invalid.
     */
    protected int validateRange(final int startIndex, int endIndex) {
        if (startIndex < 0) {
            throw new StringIndexOutOfBoundsException(startIndex);
        }
        if (endIndex > size) {
            endIndex = size;
        }
        if (startIndex > endIndex) {
            throw new StringIndexOutOfBoundsException("startIndex > endIndex");
        }
        return endIndex;
    }

}