    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.StringWriter;
    021import java.io.Writer;
    022
    023/**
    024 * {@link Writer} implementation that outputs to a {@link StringBuilder}.
    025 * <p>
    026 * <strong>NOTE:</strong> This implementation, as an alternative to {@link StringWriter}, provides an <em>un-synchronized</em> implementation for better
    027 * performance for use in a single thread. For safe usage with multiple {@link Thread}s, a {@link StringWriter} should be used.
    028 * </p>
    029 * <h2>Deprecating Serialization</h2>
    030 * <p>
    031 * <em>Serialization is deprecated and will be removed in 3.0.</em>
    032 * </p>
    033 *
    034 * @since 2.0
    035 */
    036public class StringBuilderWriter extends Writer implements Serializable {
    037
    038    private static final long serialVersionUID = -146927496096066153L;
    039
    040    /** The append target. */
    041    private final StringBuilder builder;
    042
    043    /**
    044     * Constructs a new {@link StringBuilder} instance with default capacity.
    045     */
    046    public StringBuilderWriter() {
    047        this.builder = new StringBuilder();
    048    }
    049
    050    /**
    051     * Constructs a new {@link StringBuilder} instance with the specified capacity.
    052     *
    053     * @param capacity The initial capacity of the underlying {@link StringBuilder}
    054     */
    055    public StringBuilderWriter(final int capacity) {
    056        this.builder = new StringBuilder(capacity);
    057    }
    058
    059    /**
    060     * Constructs a new instance with the specified {@link StringBuilder}.
    061     *
    062     * <p>If {@code builder} is null a new instance with default capacity will be created.</p>
    063     *
    064     * @param builder The String builder. May be null.
    065     */
    066    public StringBuilderWriter(final StringBuilder builder) {
    067        this.builder = builder != null ? builder : new StringBuilder();
    068    }
    069
    070    /**
    071     * Appends a single character to this Writer.
    072     *
    073     * @param value The character to append
    074     * @return This writer instance
    075     */
    076    @Override
    077    public Writer append(final char value) {
    078        builder.append(value);
    079        return this;
    080    }
    081
    082    /**
    083     * Appends a character sequence to this Writer.
    084     *
    085     * @param value The character to append
    086     * @return This writer instance
    087     */
    088    @Override
    089    public Writer append(final CharSequence value) {
    090        builder.append(value);
    091        return this;
    092    }
    093
    094    /**
    095     * Appends a portion of a character sequence to the {@link StringBuilder}.
    096     *
    097     * @param value The character to append
    098     * @param start The index of the first character
    099     * @param end The index of the last character + 1
    100     * @return This writer instance
    101     */
    102    @Override
    103    public Writer append(final CharSequence value, final int start, final int end) {
    104        builder.append(value, start, end);
    105        return this;
    106    }
    107
    108    /**
    109     * Closing this writer has no effect.
    110     */
    111    @Override
    112    public void close() {
    113        // no-op
    114    }
    115
    116    /**
    117     * Flushing this writer has no effect.
    118     */
    119    @Override
    120    public void flush() {
    121        // no-op
    122    }
    123
    124    /**
    125     * Gets the underlying builder.
    126     *
    127     * @return The underlying builder
    128     */
    129    public StringBuilder getBuilder() {
    130        return builder;
    131    }
    132
    133    /**
    134     * Returns {@link StringBuilder#toString()}.
    135     *
    136     * @return The contents of the String builder.
    137     */
    138    @Override
    139    public String toString() {
    140        return builder.toString();
    141    }
    142
    143    /**
    144     * Writes a portion of a character array to the {@link StringBuilder}.
    145     *
    146     * @param value The value to write
    147     * @param offset The index of the first character
    148     * @param length The number of characters to write
    149     */
    150    @Override
    151    public void write(final char[] value, final int offset, final int length) {
    152        if (value != null) {
    153            builder.append(value, offset, length);
    154        }
    155    }
    156
    157    /**
    158     * Writes a String to the {@link StringBuilder}.
    159     *
    160     * @param value The value to write
    161     */
    162    @Override
    163    public void write(final String value) {
    164        if (value != null) {
    165            builder.append(value);
    166        }
    167    }
    168}