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1   /*
2    * Copyright (c) 1996, 2004, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package java.io;
27  
28  
29  /**
30   * A character stream that collects its output in a string buffer, which can
31   * then be used to construct a string.
32   * <p>
33   * Closing a <tt>StringWriter</tt> has no effect. The methods in this class
34   * can be called after the stream has been closed without generating an
35   * <tt>IOException</tt>.
36   *
37   * @author      Mark Reinhold
38   * @since       JDK1.1
39   */
40  
41  public class StringWriter extends Writer {
42  
43      private StringBuffer buf;
44  
45      /**
46       * Create a new string writer using the default initial string-buffer
47       * size.
48       */
49      public StringWriter() {
50          buf = new StringBuffer();
51          lock = buf;
52      }
53  
54      /**
55       * Create a new string writer using the specified initial string-buffer
56       * size.
57       *
58       * @param initialSize
59       *        The number of <tt>char</tt> values that will fit into this buffer
60       *        before it is automatically expanded
61       *
62       * @throws IllegalArgumentException
63       *         If <tt>initialSize</tt> is negative
64       */
65      public StringWriter(int initialSize) {
66          if (initialSize < 0) {
67              throw new IllegalArgumentException("Negative buffer size");
68          }
69          buf = new StringBuffer(initialSize);
70          lock = buf;
71      }
72  
73      /**
74       * Write a single character.
75       */
76      public void write(int c) {
77          buf.append((char) c);
78      }
79  
80      /**
81       * Write a portion of an array of characters.
82       *
83       * @param  cbuf  Array of characters
84       * @param  off   Offset from which to start writing characters
85       * @param  len   Number of characters to write
86       */
87      public void write(char cbuf[], int off, int len) {
88          if ((off < 0) || (off > cbuf.length) || (len < 0) ||
89              ((off + len) > cbuf.length) || ((off + len) < 0)) {
90              throw new IndexOutOfBoundsException();
91          } else if (len == 0) {
92              return;
93          }
94          buf.append(cbuf, off, len);
95      }
96  
97      /**
98       * Write a string.
99       */
100     public void write(String str) {
101         buf.append(str);
102     }
103 
104     /**
105      * Write a portion of a string.
106      *
107      * @param  str  String to be written
108      * @param  off  Offset from which to start writing characters
109      * @param  len  Number of characters to write
110      */
111     public void write(String str, int off, int len)  {
112         buf.append(str.substring(off, off + len));
113     }
114 
115     /**
116      * Appends the specified character sequence to this writer.
117      *
118      * <p> An invocation of this method of the form <tt>out.append(csq)</tt>
119      * behaves in exactly the same way as the invocation
120      *
121      * <pre>
122      *     out.write(csq.toString()) </pre>
123      *
124      * <p> Depending on the specification of <tt>toString</tt> for the
125      * character sequence <tt>csq</tt>, the entire sequence may not be
126      * appended. For instance, invoking the <tt>toString</tt> method of a
127      * character buffer will return a subsequence whose content depends upon
128      * the buffer's position and limit.
129      *
130      * @param  csq
131      *         The character sequence to append.  If <tt>csq</tt> is
132      *         <tt>null</tt>, then the four characters <tt>"null"</tt> are
133      *         appended to this writer.
134      *
135      * @return  This writer
136      *
137      * @since  1.5
138      */
139     public StringWriter append(CharSequence csq) {
140         if (csq == null)
141             write("null");
142         else
143             write(csq.toString());
144         return this;
145     }
146 
147     /**
148      * Appends a subsequence of the specified character sequence to this writer.
149      *
150      * <p> An invocation of this method of the form <tt>out.append(csq, start,
151      * end)</tt> when <tt>csq</tt> is not <tt>null</tt>, behaves in
152      * exactly the same way as the invocation
153      *
154      * <pre>
155      *     out.write(csq.subSequence(start, end).toString()) </pre>
156      *
157      * @param  csq
158      *         The character sequence from which a subsequence will be
159      *         appended.  If <tt>csq</tt> is <tt>null</tt>, then characters
160      *         will be appended as if <tt>csq</tt> contained the four
161      *         characters <tt>"null"</tt>.
162      *
163      * @param  start
164      *         The index of the first character in the subsequence
165      *
166      * @param  end
167      *         The index of the character following the last character in the
168      *         subsequence
169      *
170      * @return  This writer
171      *
172      * @throws  IndexOutOfBoundsException
173      *          If <tt>start</tt> or <tt>end</tt> are negative, <tt>start</tt>
174      *          is greater than <tt>end</tt>, or <tt>end</tt> is greater than
175      *          <tt>csq.length()</tt>
176      *
177      * @since  1.5
178      */
179     public StringWriter append(CharSequence csq, int start, int end) {
180         CharSequence cs = (csq == null ? "null" : csq);
181         write(cs.subSequence(start, end).toString());
182         return this;
183     }
184 
185     /**
186      * Appends the specified character to this writer.
187      *
188      * <p> An invocation of this method of the form <tt>out.append(c)</tt>
189      * behaves in exactly the same way as the invocation
190      *
191      * <pre>
192      *     out.write(c) </pre>
193      *
194      * @param  c
195      *         The 16-bit character to append
196      *
197      * @return  This writer
198      *
199      * @since 1.5
200      */
201     public StringWriter append(char c) {
202         write(c);
203         return this;
204     }
205 
206     /**
207      * Return the buffer's current value as a string.
208      */
209     public String toString() {
210         return buf.toString();
211     }
212 
213     /**
214      * Return the string buffer itself.
215      *
216      * @return StringBuffer holding the current buffer value.
217      */
218     public StringBuffer getBuffer() {
219         return buf;
220     }
221 
222     /**
223      * Flush the stream.
224      */
225     public void flush() {
226     }
227 
228     /**
229      * Closing a <tt>StringWriter</tt> has no effect. The methods in this
230      * class can be called after the stream has been closed without generating
231      * an <tt>IOException</tt>.
232      */
233     public void close() throws IOException {
234     }
235 
236 }