    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.io.output;
    018
    019import java.io.Serializable;
    020import java.io.Writer;
    021
    022/**
    023 * {@link Writer} implementation that outputs to a {@link StringBuilder}.
    024 * <p>
    025 * <strong>NOTE:</strong> This implementation, as an alternative to
    026 * {@link java.io.StringWriter}, provides an <i>un-synchronized</i>
    027 * (i.e. for use in a single thread) implementation for better performance.
    028 * For safe usage with multiple {@link Thread}s then
    029 * {@link java.io.StringWriter} should be used.
    030 * </p>
    031 * <h2>Deprecating Serialization</h2>
    032 * <p>
    033 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    034 * </p>
    035 * @since 2.0
    036 */
    037public class StringBuilderWriter extends Writer implements Serializable {
    038
    039    private static final long serialVersionUID = -146927496096066153L;
    040
    041    /** The append target. */
    042    private final StringBuilder builder;
    043
    044    /**
    045     * Constructs a new {@link StringBuilder} instance with default capacity.
    046     */
    047    public StringBuilderWriter() {
    048        this.builder = new StringBuilder();
    049    }
    050
    051    /**
    052     * Constructs a new {@link StringBuilder} instance with the specified capacity.
    053     *
    054     * @param capacity The initial capacity of the underlying {@link StringBuilder}
    055     */
    056    public StringBuilderWriter(final int capacity) {
    057        this.builder = new StringBuilder(capacity);
    058    }
    059
    060    /**
    061     * Constructs a new instance with the specified {@link StringBuilder}.
    062     *
    063     * <p>If {@code builder} is null a new instance with default capacity will be created.</p>
    064     *
    065     * @param builder The String builder. May be null.
    066     */
    067    public StringBuilderWriter(final StringBuilder builder) {
    068        this.builder = builder != null ? builder : new StringBuilder();
    069    }
    070
    071    /**
    072     * Appends a single character to this Writer.
    073     *
    074     * @param value The character to append
    075     * @return This writer instance
    076     */
    077    @Override
    078    public Writer append(final char value) {
    079        builder.append(value);
    080        return this;
    081    }
    082
    083    /**
    084     * Appends a character sequence to this Writer.
    085     *
    086     * @param value The character to append
    087     * @return This writer instance
    088     */
    089    @Override
    090    public Writer append(final CharSequence value) {
    091        builder.append(value);
    092        return this;
    093    }
    094
    095    /**
    096     * Appends a portion of a character sequence to the {@link StringBuilder}.
    097     *
    098     * @param value The character to append
    099     * @param start The index of the first character
    100     * @param end The index of the last character + 1
    101     * @return This writer instance
    102     */
    103    @Override
    104    public Writer append(final CharSequence value, final int start, final int end) {
    105        builder.append(value, start, end);
    106        return this;
    107    }
    108
    109    /**
    110     * Closing this writer has no effect.
    111     */
    112    @Override
    113    public void close() {
    114        // no-op
    115    }
    116
    117    /**
    118     * Flushing this writer has no effect.
    119     */
    120    @Override
    121    public void flush() {
    122        // no-op
    123    }
    124
    125    /**
    126     * Gets the underlying builder.
    127     *
    128     * @return The underlying builder
    129     */
    130    public StringBuilder getBuilder() {
    131        return builder;
    132    }
    133
    134    /**
    135     * Returns {@link StringBuilder#toString()}.
    136     *
    137     * @return The contents of the String builder.
    138     */
    139    @Override
    140    public String toString() {
    141        return builder.toString();
    142    }
    143
    144    /**
    145     * Writes a portion of a character array to the {@link StringBuilder}.
    146     *
    147     * @param value The value to write
    148     * @param offset The index of the first character
    149     * @param length The number of characters to write
    150     */
    151    @Override
    152    public void write(final char[] value, final int offset, final int length) {
    153        if (value != null) {
    154            builder.append(value, offset, length);
    155        }
    156    }
    157
    158    /**
    159     * Writes a String to the {@link StringBuilder}.
    160     *
    161     * @param value The value to write
    162     */
    163    @Override
    164    public void write(final String value) {
    165        if (value != null) {
    166            builder.append(value);
    167        }
    168    }
    169}