1 /*
2 * Copyright (c) 1996, 2016, 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 {@code StringWriter} has no effect. The methods in this class
34 * can be called after the stream has been closed without generating an
35 * {@code IOException}.
36 *
37 * @author Mark Reinhold
38 * @since 1.1
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 {@code char} values that will fit into this buffer
60 * before it is automatically expanded
61 *
62 * @throws IllegalArgumentException
63 * If {@code initialSize} 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 * @throws IndexOutOfBoundsException
88 * If {@code off} is negative, or {@code len} is negative,
89 * or {@code off + len} is negative or greater than the length
90 * of the given array
91 */
92 public void write(char cbuf[], int off, int len) {
93 if ((off < 0) || (off > cbuf.length) || (len < 0) ||
94 ((off + len) > cbuf.length) || ((off + len) < 0)) {
95 throw new IndexOutOfBoundsException();
96 } else if (len == 0) {
97 return;
98 }
99 buf.append(cbuf, off, len);
100 }
101
102 /**
103 * Write a string.
104 */
105 public void write(String str) {
106 buf.append(str);
107 }
108
109 /**
110 * Write a portion of a string.
111 *
112 * @param str String to be written
113 * @param off Offset from which to start writing characters
114 * @param len Number of characters to write
115 *
116 * @throws IndexOutOfBoundsException
117 * If {@code off} is negative, or {@code len} is negative,
118 * or {@code off + len} is negative or greater than the length
119 * of the given string
120 */
121 public void write(String str, int off, int len) {
122 buf.append(str, off, off + len);
123 }
124
125 /**
126 * Appends the specified character sequence to this writer.
127 *
128 * <p> An invocation of this method of the form {@code out.append(csq)}
129 * behaves in exactly the same way as the invocation
130 *
131 * <pre>
132 * out.write(csq.toString()) </pre>
133 *
134 * <p> Depending on the specification of {@code toString} for the
135 * character sequence {@code csq}, the entire sequence may not be
136 * appended. For instance, invoking the {@code toString} method of a
137 * character buffer will return a subsequence whose content depends upon
138 * the buffer's position and limit.
139 *
140 * @param csq
141 * The character sequence to append. If {@code csq} is
142 * {@code null}, then the four characters "{@code null}" are
143 * appended to this writer.
144 *
145 * @return This writer
146 *
147 * @since 1.5
148 */
149 public StringWriter append(CharSequence csq) {
150 if (csq == null)
151 write("null");
152 else
153 write(csq.toString());
154 return this;
155 }
156
157 /**
158 * Appends a subsequence of the specified character sequence to this writer.
159 *
160 * <p> An invocation of this method of the form
161 * {@code out.append(csq, start, end)} when {@code csq}
162 * is not {@code null}, behaves in
163 * exactly the same way as the invocation
164 *
165 * <pre>{@code
166 * out.write(csq.subSequence(start, end).toString())
167 * }</pre>
168 *
169 * @param csq
170 * The character sequence from which a subsequence will be
171 * appended. If {@code csq} is {@code null}, then characters
172 * will be appended as if {@code csq} contained the four
173 * characters "{@code null}".
174 *
175 * @param start
176 * The index of the first character in the subsequence
177 *
178 * @param end
179 * The index of the character following the last character in the
180 * subsequence
181 *
182 * @return This writer
183 *
184 * @throws IndexOutOfBoundsException
185 * If {@code start} or {@code end} are negative, {@code start}
186 * is greater than {@code end}, or {@code end} is greater than
187 * {@code csq.length()}
188 *
189 * @since 1.5
190 */
191 public StringWriter append(CharSequence csq, int start, int end) {
192 CharSequence cs = (csq == null ? "null" : csq);
193 write(cs.subSequence(start, end).toString());
194 return this;
195 }
196
197 /**
198 * Appends the specified character to this writer.
199 *
200 * <p> An invocation of this method of the form {@code out.append(c)}
201 * behaves in exactly the same way as the invocation
202 *
203 * <pre>
204 * out.write(c) </pre>
205 *
206 * @param c
207 * The 16-bit character to append
208 *
209 * @return This writer
210 *
211 * @since 1.5
212 */
213 public StringWriter append(char c) {
214 write(c);
215 return this;
216 }
217
218 /**
219 * Return the buffer's current value as a string.
220 */
221 public String toString() {
222 return buf.toString();
223 }
224
225 /**
226 * Return the string buffer itself.
227 *
228 * @return StringBuffer holding the current buffer value.
229 */
230 public StringBuffer getBuffer() {
231 return buf;
232 }
233
234 /**
235 * Flush the stream.
236 */
237 public void flush() {
238 }
239
240 /**
241 * Closing a {@code StringWriter} has no effect. The methods in this
242 * class can be called after the stream has been closed without generating
243 * an {@code IOException}.
244 */
245 public void close() throws IOException {
246 }
247
248 }