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 * @version $Id: StringBuilderWriter.java 1304052 2012-03-22 20:55:29Z ggregory $
032 * @since 2.0
033 */
034public class StringBuilderWriter extends Writer implements Serializable {
035
036    private final StringBuilder builder;
037
038    /**
039     * Construct a new {@link StringBuilder} instance with default capacity.
040     */
041    public StringBuilderWriter() {
042        this.builder = new StringBuilder();
043    }
044
045    /**
046     * Construct 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(int capacity) {
051        this.builder = new StringBuilder(capacity);
052    }
053
054    /**
055     * Construct a new instance with the specified {@link StringBuilder}.
056     *
057     * @param builder The String builder
058     */
059    public StringBuilderWriter(StringBuilder builder) {
060        this.builder = builder != null ? builder : new StringBuilder();
061    }
062
063    /**
064     * Append a single character to this Writer.
065     *
066     * @param value The character to append
067     * @return This writer instance
068     */
069    @Override
070    public Writer append(char value) {
071        builder.append(value);
072        return this;
073    }
074
075    /**
076     * Append a character sequence to this Writer.
077     *
078     * @param value The character to append
079     * @return This writer instance
080     */
081    @Override
082    public Writer append(CharSequence value) {
083        builder.append(value);
084        return this;
085    }
086
087    /**
088     * Append a portion of a character sequence to the {@link StringBuilder}.
089     *
090     * @param value The character to append
091     * @param start The index of the first character
092     * @param end The index of the last character + 1
093     * @return This writer instance
094     */
095    @Override
096    public Writer append(CharSequence value, int start, int end) {
097        builder.append(value, start, end);
098        return this;
099    }
100
101    /**
102     * Closing this writer has no effect. 
103     */
104    @Override
105    public void close() {
106    }
107
108    /**
109     * Flushing this writer has no effect. 
110     */
111    @Override
112    public void flush() {
113    }
114
115
116    /**
117     * Write a String to the {@link StringBuilder}.
118     * 
119     * @param value The value to write
120     */
121    @Override
122    public void write(String value) {
123        if (value != null) {
124            builder.append(value);
125        }
126    }
127
128    /**
129     * Write a portion of a character array to the {@link StringBuilder}.
130     *
131     * @param value The value to write
132     * @param offset The index of the first character
133     * @param length The number of characters to write
134     */
135    @Override
136    public void write(char[] value, int offset, int length) {
137        if (value != null) {
138            builder.append(value, offset, length);
139        }
140    }
141
142    /**
143     * Return the underlying builder.
144     *
145     * @return The underlying builder
146     */
147    public StringBuilder getBuilder() {
148        return builder;
149    }
150
151    /**
152     * Returns {@link StringBuilder#toString()}.
153     *
154     * @return The contents of the String builder.
155     */
156    @Override
157    public String toString() {
158        return builder.toString();
159    }
160}