1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.io.output;
18
19 import java.io.Serializable;
20 import java.io.Writer;
21
22 /**
23 * {@link Writer} implementation that outputs to a {@link StringBuilder}.
24 * <p>
25 * <strong>NOTE:</strong> This implementation, as an alternative to
26 * {@code java.io.StringWriter}, provides an <i>un-synchronized</i>
27 * (i.e. for use in a single thread) implementation for better performance.
28 * For safe usage with multiple {@link Thread}s then
29 * {@code java.io.StringWriter} should be used.
30 * </p>
31 *
32 * @since 2.0
33 */
34 public class StringBuilderWriter extends Writer implements Serializable {
35
36 private static final long serialVersionUID = -146927496096066153L;
37 private final StringBuilder builder;
38
39 /**
40 * Constructs a new {@link StringBuilder} instance with default capacity.
41 */
42 public StringBuilderWriter() {
43 this.builder = new StringBuilder();
44 }
45
46 /**
47 * Constructs a new {@link StringBuilder} instance with the specified capacity.
48 *
49 * @param capacity The initial capacity of the underlying {@link StringBuilder}
50 */
51 public StringBuilderWriter(final int capacity) {
52 this.builder = new StringBuilder(capacity);
53 }
54
55 /**
56 * Constructs a new instance with the specified {@link StringBuilder}.
57 *
58 * <p>If {@code builder} is null a new instance with default capacity will be created.</p>
59 *
60 * @param builder The String builder. May be null.
61 */
62 public StringBuilderWriter(final StringBuilder builder) {
63 this.builder = builder != null ? builder : new StringBuilder();
64 }
65
66 /**
67 * Appends a single character to this Writer.
68 *
69 * @param value The character to append
70 * @return This writer instance
71 */
72 @Override
73 public Writer append(final char value) {
74 builder.append(value);
75 return this;
76 }
77
78 /**
79 * Appends a character sequence to this Writer.
80 *
81 * @param value The character to append
82 * @return This writer instance
83 */
84 @Override
85 public Writer append(final CharSequence value) {
86 builder.append(value);
87 return this;
88 }
89
90 /**
91 * Appends a portion of a character sequence to the {@link StringBuilder}.
92 *
93 * @param value The character to append
94 * @param start The index of the first character
95 * @param end The index of the last character + 1
96 * @return This writer instance
97 */
98 @Override
99 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 }