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