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