View Javadoc
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   * <h2>Deprecating Serialization</h2>
32   * <p>
33   * <em>Serialization is deprecated and will be removed in 3.0.</em>
34   * </p>
35   * @since 2.0
36   */
37  public class StringBuilderWriter extends Writer implements Serializable {
38  
39      private static final long serialVersionUID = -146927496096066153L;
40      private final StringBuilder builder;
41  
42      /**
43       * Constructs a new {@link StringBuilder} instance with default capacity.
44       */
45      public StringBuilderWriter() {
46          this.builder = new StringBuilder();
47      }
48  
49      /**
50       * Constructs a new {@link StringBuilder} instance with the specified capacity.
51       *
52       * @param capacity The initial capacity of the underlying {@link StringBuilder}
53       */
54      public StringBuilderWriter(final int capacity) {
55          this.builder = new StringBuilder(capacity);
56      }
57  
58      /**
59       * Constructs a new instance with the specified {@link StringBuilder}.
60       *
61       * <p>If {@code builder} is null a new instance with default capacity will be created.</p>
62       *
63       * @param builder The String builder. May be null.
64       */
65      public StringBuilderWriter(final StringBuilder builder) {
66          this.builder = builder != null ? builder : new StringBuilder();
67      }
68  
69      /**
70       * Appends a single character to this Writer.
71       *
72       * @param value The character to append
73       * @return This writer instance
74       */
75      @Override
76      public Writer append(final char value) {
77          builder.append(value);
78          return this;
79      }
80  
81      /**
82       * Appends a character sequence to this Writer.
83       *
84       * @param value The character to append
85       * @return This writer instance
86       */
87      @Override
88      public Writer append(final CharSequence value) {
89          builder.append(value);
90          return this;
91      }
92  
93      /**
94       * Appends a portion of a character sequence to the {@link StringBuilder}.
95       *
96       * @param value The character to append
97       * @param start The index of the first character
98       * @param end The index of the last character + 1
99       * @return This writer instance
100      */
101     @Override
102     public Writer append(final CharSequence value, final int start, final int end) {
103         builder.append(value, start, end);
104         return this;
105     }
106 
107     /**
108      * Closing this writer has no effect.
109      */
110     @Override
111     public void close() {
112         // no-op
113     }
114 
115     /**
116      * Flushing this writer has no effect.
117      */
118     @Override
119     public void flush() {
120         // no-op
121     }
122 
123 
124     /**
125      * Returns 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 }