1 /*
2 * Copyright (c) 1996, 2011, 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 * Abstract class for writing to character streams. The only methods that a
31 * subclass must implement are write(char[], int, int), flush(), and close().
32 * Most subclasses, however, will override some of the methods defined here in
33 * order to provide higher efficiency, additional functionality, or both.
34 *
35 * @see Writer
36 * @see BufferedWriter
37 * @see CharArrayWriter
38 * @see FilterWriter
39 * @see OutputStreamWriter
40 * @see FileWriter
41 * @see PipedWriter
42 * @see PrintWriter
43 * @see StringWriter
44 * @see Reader
45 *
46 * @author Mark Reinhold
47 * @since JDK1.1
48 */
49
50 public abstract class Writer implements Appendable, Closeable, Flushable {
51
52 /**
53 * Temporary buffer used to hold writes of strings and single characters
54 */
55 private char[] writeBuffer;
56
57 /**
58 * Size of writeBuffer, must be >= 1
59 */
60 private static final int WRITE_BUFFER_SIZE = 1024;
61
62 /**
63 * The object used to synchronize operations on this stream. For
64 * efficiency, a character-stream object may use an object other than
65 * itself to protect critical sections. A subclass should therefore use
66 * the object in this field rather than <tt>this</tt> or a synchronized
67 * method.
68 */
69 protected Object lock;
70
71 /**
72 * Creates a new character-stream writer whose critical sections will
73 * synchronize on the writer itself.
74 */
75 protected Writer() {
76 this.lock = this;
77 }
78
79 /**
80 * Creates a new character-stream writer whose critical sections will
81 * synchronize on the given object.
82 *
83 * @param lock
84 * Object to synchronize on
85 */
86 protected Writer(Object lock) {
87 if (lock == null) {
88 throw new NullPointerException();
89 }
90 this.lock = lock;
91 }
92
93 /**
94 * Writes a single character. The character to be written is contained in
95 * the 16 low-order bits of the given integer value; the 16 high-order bits
96 * are ignored.
97 *
98 * <p> Subclasses that intend to support efficient single-character output
99 * should override this method.
100 *
101 * @param c
102 * int specifying a character to be written
103 *
104 * @throws IOException
105 * If an I/O error occurs
106 */
107 public void write(int c) throws IOException {
108 synchronized (lock) {
109 if (writeBuffer == null){
110 writeBuffer = new char[WRITE_BUFFER_SIZE];
111 }
112 writeBuffer[0] = (char) c;
113 write(writeBuffer, 0, 1);
114 }
115 }
116
117 /**
118 * Writes an array of characters.
119 *
120 * @param cbuf
121 * Array of characters to be written
122 *
123 * @throws IOException
124 * If an I/O error occurs
125 */
126 public void write(char cbuf[]) throws IOException {
127 write(cbuf, 0, cbuf.length);
128 }
129
130 /**
131 * Writes a portion of an array of characters.
132 *
133 * @param cbuf
134 * Array of characters
135 *
136 * @param off
137 * Offset from which to start writing characters
138 *
139 * @param len
140 * Number of characters to write
141 *
142 * @throws IOException
143 * If an I/O error occurs
144 */
145 abstract public void write(char cbuf[], int off, int len) throws IOException;
146
147 /**
148 * Writes a string.
149 *
150 * @param str
151 * String to be written
152 *
153 * @throws IOException
154 * If an I/O error occurs
155 */
156 public void write(String str) throws IOException {
157 write(str, 0, str.length());
158 }
159
160 /**
161 * Writes a portion of a string.
162 *
163 * @param str
164 * A String
165 *
166 * @param off
167 * Offset from which to start writing characters
168 *
169 * @param len
170 * Number of characters to write
171 *
172 * @throws IndexOutOfBoundsException
173 * If <tt>off</tt> is negative, or <tt>len</tt> is negative,
174 * or <tt>off+len</tt> is negative or greater than the length
175 * of the given string
176 *
177 * @throws IOException
178 * If an I/O error occurs
179 */
180 public void write(String str, int off, int len) throws IOException {
181 synchronized (lock) {
182 char cbuf[];
183 if (len <= WRITE_BUFFER_SIZE) {
184 if (writeBuffer == null) {
185 writeBuffer = new char[WRITE_BUFFER_SIZE];
186 }
187 cbuf = writeBuffer;
188 } else { // Don't permanently allocate very large buffers.
189 cbuf = new char[len];
190 }
191 str.getChars(off, (off + len), cbuf, 0);
192 write(cbuf, 0, len);
193 }
194 }
195
196 /**
197 * Appends the specified character sequence to this writer.
198 *
199 * <p> An invocation of this method of the form <tt>out.append(csq)</tt>
200 * behaves in exactly the same way as the invocation
201 *
202 * <pre>
203 * out.write(csq.toString()) </pre>
204 *
205 * <p> Depending on the specification of <tt>toString</tt> for the
206 * character sequence <tt>csq</tt>, the entire sequence may not be
207 * appended. For instance, invoking the <tt>toString</tt> method of a
208 * character buffer will return a subsequence whose content depends upon
209 * the buffer's position and limit.
210 *
211 * @param csq
212 * The character sequence to append. If <tt>csq</tt> is
213 * <tt>null</tt>, then the four characters <tt>"null"</tt> are
214 * appended to this writer.
215 *
216 * @return This writer
217 *
218 * @throws IOException
219 * If an I/O error occurs
220 *
221 * @since 1.5
222 */
223 public Writer append(CharSequence csq) throws IOException {
224 if (csq == null)
225 write("null");
226 else
227 write(csq.toString());
228 return this;
229 }
230
231 /**
232 * Appends a subsequence of the specified character sequence to this writer.
233 * <tt>Appendable</tt>.
234 *
235 * <p> An invocation of this method of the form <tt>out.append(csq, start,
236 * end)</tt> when <tt>csq</tt> is not <tt>null</tt> behaves in exactly the
237 * same way as the invocation
238 *
239 * <pre>
240 * out.write(csq.subSequence(start, end).toString()) </pre>
241 *
242 * @param csq
243 * The character sequence from which a subsequence will be
244 * appended. If <tt>csq</tt> is <tt>null</tt>, then characters
245 * will be appended as if <tt>csq</tt> contained the four
246 * characters <tt>"null"</tt>.
247 *
248 * @param start
249 * The index of the first character in the subsequence
250 *
251 * @param end
252 * The index of the character following the last character in the
253 * subsequence
254 *
255 * @return This writer
256 *
257 * @throws IndexOutOfBoundsException
258 * If <tt>start</tt> or <tt>end</tt> are negative, <tt>start</tt>
259 * is greater than <tt>end</tt>, or <tt>end</tt> is greater than
260 * <tt>csq.length()</tt>
261 *
262 * @throws IOException
263 * If an I/O error occurs
264 *
265 * @since 1.5
266 */
267 public Writer append(CharSequence csq, int start, int end) throws IOException {
268 CharSequence cs = (csq == null ? "null" : csq);
269 write(cs.subSequence(start, end).toString());
270 return this;
271 }
272
273 /**
274 * Appends the specified character to this writer.
275 *
276 * <p> An invocation of this method of the form <tt>out.append(c)</tt>
277 * behaves in exactly the same way as the invocation
278 *
279 * <pre>
280 * out.write(c) </pre>
281 *
282 * @param c
283 * The 16-bit character to append
284 *
285 * @return This writer
286 *
287 * @throws IOException
288 * If an I/O error occurs
289 *
290 * @since 1.5
291 */
292 public Writer append(char c) throws IOException {
293 write(c);
294 return this;
295 }
296
297 /**
298 * Flushes the stream. If the stream has saved any characters from the
299 * various write() methods in a buffer, write them immediately to their
300 * intended destination. Then, if that destination is another character or
301 * byte stream, flush it. Thus one flush() invocation will flush all the
302 * buffers in a chain of Writers and OutputStreams.
303 *
304 * <p> If the intended destination of this stream is an abstraction provided
305 * by the underlying operating system, for example a file, then flushing the
306 * stream guarantees only that bytes previously written to the stream are
307 * passed to the operating system for writing; it does not guarantee that
308 * they are actually written to a physical device such as a disk drive.
309 *
310 * @throws IOException
311 * If an I/O error occurs
312 */
313 abstract public void flush() throws IOException;
314
315 /**
316 * Closes the stream, flushing it first. Once the stream has been closed,
317 * further write() or flush() invocations will cause an IOException to be
318 * thrown. Closing a previously closed stream has no effect.
319 *
320 * @throws IOException
321 * If an I/O error occurs
322 */
323 abstract public void close() throws IOException;
324
325 }