1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36 package java.util.concurrent.atomic;
37
38 import java.lang.invoke.MethodHandles;
39 import java.lang.invoke.VarHandle;
40
41 /**
42 * A {@code boolean} value that may be updated atomically. See the
43 * {@link VarHandle} specification for descriptions of the properties
44 * of atomic accesses. An {@code AtomicBoolean} is used in
45 * applications such as atomically updated flags, and cannot be used
46 * as a replacement for a {@link java.lang.Boolean}.
47 *
48 * @since 1.5
49 * @author Doug Lea
50 */
51 public class AtomicBoolean implements java.io.Serializable {
52 private static final long serialVersionUID = 4654671469794556979L;
53 private static final VarHandle VALUE;
54 static {
55 try {
56 MethodHandles.Lookup l = MethodHandles.lookup();
57 VALUE = l.findVarHandle(AtomicBoolean.class, "value", int.class);
58 } catch (ReflectiveOperationException e) {
59 throw new ExceptionInInitializerError(e);
60 }
61 }
62
63 private volatile int value;
64
65 /**
66 * Creates a new {@code AtomicBoolean} with the given initial value.
67 *
68 * @param initialValue the initial value
69 */
70 public AtomicBoolean(boolean initialValue) {
71 value = initialValue ? 1 : 0;
72 }
73
74 /**
75 * Creates a new {@code AtomicBoolean} with initial value {@code false}.
76 */
77 public AtomicBoolean() {
78 }
79
80 /**
81 * Returns the current value,
82 * with memory effects as specified by {@link VarHandle#getVolatile}.
83 *
84 * @return the current value
85 */
86 public final boolean get() {
87 return value != 0;
88 }
89
90 /**
91 * Atomically sets the value to {@code newValue}
92 * if the current value {@code == expectedValue},
93 * with memory effects as specified by {@link VarHandle#compareAndSet}.
94 *
95 * @param expectedValue the expected value
96 * @param newValue the new value
97 * @return {@code true} if successful. False return indicates that
98 * the actual value was not equal to the expected value.
99 */
100 public final boolean compareAndSet(boolean expectedValue, boolean newValue) {
101 return VALUE.compareAndSet(this,
102 (expectedValue ? 1 : 0),
103 (newValue ? 1 : 0));
104 }
105
106 /**
107 * Possibly atomically sets the value to {@code newValue}
108 * if the current value {@code == expectedValue},
109 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
110 *
111 * @deprecated This method has plain memory effects but the method
112 * name implies volatile memory effects (see methods such as
113 * {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
114 * confusion over plain or volatile memory effects it is recommended that
115 * the method {@link #weakCompareAndSetPlain} be used instead.
116 *
117 * @param expectedValue the expected value
118 * @param newValue the new value
119 * @return {@code true} if successful
120 * @see #weakCompareAndSetPlain
121 */
122 @Deprecated(since="9")
123 public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {
124 return VALUE.weakCompareAndSetPlain(this,
125 (expectedValue ? 1 : 0),
126 (newValue ? 1 : 0));
127 }
128
129 /**
130 * Possibly atomically sets the value to {@code newValue}
131 * if the current value {@code == expectedValue},
132 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
133 *
134 * @param expectedValue the expected value
135 * @param newValue the new value
136 * @return {@code true} if successful
137 * @since 9
138 */
139 public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {
140 return VALUE.weakCompareAndSetPlain(this,
141 (expectedValue ? 1 : 0),
142 (newValue ? 1 : 0));
143 }
144
145 /**
146 * Sets the value to {@code newValue},
147 * with memory effects as specified by {@link VarHandle#setVolatile}.
148 *
149 * @param newValue the new value
150 */
151 public final void set(boolean newValue) {
152 value = newValue ? 1 : 0;
153 }
154
155 /**
156 * Sets the value to {@code newValue},
157 * with memory effects as specified by {@link VarHandle#setRelease}.
158 *
159 * @param newValue the new value
160 * @since 1.6
161 */
162 public final void lazySet(boolean newValue) {
163 VALUE.setRelease(this, (newValue ? 1 : 0));
164 }
165
166 /**
167 * Atomically sets the value to {@code newValue} and returns the old value,
168 * with memory effects as specified by {@link VarHandle#getAndSet}.
169 *
170 * @param newValue the new value
171 * @return the previous value
172 */
173 public final boolean getAndSet(boolean newValue) {
174 return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;
175 }
176
177 /**
178 * Returns the String representation of the current value.
179 * @return the String representation of the current value
180 */
181 public String toString() {
182 return Boolean.toString(get());
183 }
184
185 // jdk9
186
187 /**
188 * Returns the current value, with memory semantics of reading as
189 * if the variable was declared non-{@code volatile}.
190 *
191 * @return the value
192 * @since 9
193 */
194 public final boolean getPlain() {
195 return (int)VALUE.get(this) != 0;
196 }
197
198 /**
199 * Sets the value to {@code newValue}, with memory semantics
200 * of setting as if the variable was declared non-{@code volatile}
201 * and non-{@code final}.
202 *
203 * @param newValue the new value
204 * @since 9
205 */
206 public final void setPlain(boolean newValue) {
207 VALUE.set(this, newValue ? 1 : 0);
208 }
209
210 /**
211 * Returns the current value,
212 * with memory effects as specified by {@link VarHandle#getOpaque}.
213 *
214 * @return the value
215 * @since 9
216 */
217 public final boolean getOpaque() {
218 return (int)VALUE.getOpaque(this) != 0;
219 }
220
221 /**
222 * Sets the value to {@code newValue},
223 * with memory effects as specified by {@link VarHandle#setOpaque}.
224 *
225 * @param newValue the new value
226 * @since 9
227 */
228 public final void setOpaque(boolean newValue) {
229 VALUE.setOpaque(this, newValue ? 1 : 0);
230 }
231
232 /**
233 * Returns the current value,
234 * with memory effects as specified by {@link VarHandle#getAcquire}.
235 *
236 * @return the value
237 * @since 9
238 */
239 public final boolean getAcquire() {
240 return (int)VALUE.getAcquire(this) != 0;
241 }
242
243 /**
244 * Sets the value to {@code newValue},
245 * with memory effects as specified by {@link VarHandle#setRelease}.
246 *
247 * @param newValue the new value
248 * @since 9
249 */
250 public final void setRelease(boolean newValue) {
251 VALUE.setRelease(this, newValue ? 1 : 0);
252 }
253
254 /**
255 * Atomically sets the value to {@code newValue} if the current value,
256 * referred to as the <em>witness value</em>, {@code == expectedValue},
257 * with memory effects as specified by
258 * {@link VarHandle#compareAndExchange}.
259 *
260 * @param expectedValue the expected value
261 * @param newValue the new value
262 * @return the witness value, which will be the same as the
263 * expected value if successful
264 * @since 9
265 */
266 public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {
267 return (int)VALUE.compareAndExchange(this,
268 (expectedValue ? 1 : 0),
269 (newValue ? 1 : 0)) != 0;
270 }
271
272 /**
273 * Atomically sets the value to {@code newValue} if the current value,
274 * referred to as the <em>witness value</em>, {@code == expectedValue},
275 * with memory effects as specified by
276 * {@link VarHandle#compareAndExchangeAcquire}.
277 *
278 * @param expectedValue the expected value
279 * @param newValue the new value
280 * @return the witness value, which will be the same as the
281 * expected value if successful
282 * @since 9
283 */
284 public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {
285 return (int)VALUE.compareAndExchangeAcquire(this,
286 (expectedValue ? 1 : 0),
287 (newValue ? 1 : 0)) != 0;
288 }
289
290 /**
291 * Atomically sets the value to {@code newValue} if the current value,
292 * referred to as the <em>witness value</em>, {@code == expectedValue},
293 * with memory effects as specified by
294 * {@link VarHandle#compareAndExchangeRelease}.
295 *
296 * @param expectedValue the expected value
297 * @param newValue the new value
298 * @return the witness value, which will be the same as the
299 * expected value if successful
300 * @since 9
301 */
302 public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {
303 return (int)VALUE.compareAndExchangeRelease(this,
304 (expectedValue ? 1 : 0),
305 (newValue ? 1 : 0)) != 0;
306 }
307
308 /**
309 * Possibly atomically sets the value to {@code newValue} if the current
310 * value {@code == expectedValue},
311 * with memory effects as specified by
312 * {@link VarHandle#weakCompareAndSet}.
313 *
314 * @param expectedValue the expected value
315 * @param newValue the new value
316 * @return {@code true} if successful
317 * @since 9
318 */
319 public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {
320 return VALUE.weakCompareAndSet(this,
321 (expectedValue ? 1 : 0),
322 (newValue ? 1 : 0));
323 }
324
325 /**
326 * Possibly atomically sets the value to {@code newValue} if the current
327 * value {@code == expectedValue},
328 * with memory effects as specified by
329 * {@link VarHandle#weakCompareAndSetAcquire}.
330 *
331 * @param expectedValue the expected value
332 * @param newValue the new value
333 * @return {@code true} if successful
334 * @since 9
335 */
336 public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {
337 return VALUE.weakCompareAndSetAcquire(this,
338 (expectedValue ? 1 : 0),
339 (newValue ? 1 : 0));
340 }
341
342 /**
343 * Possibly atomically sets the value to {@code newValue} if the current
344 * value {@code == expectedValue},
345 * with memory effects as specified by
346 * {@link VarHandle#weakCompareAndSetRelease}.
347 *
348 * @param expectedValue the expected value
349 * @param newValue the new value
350 * @return {@code true} if successful
351 * @since 9
352 */
353 public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {
354 return VALUE.weakCompareAndSetRelease(this,
355 (expectedValue ? 1 : 0),
356 (newValue ? 1 : 0));
357 }
358
359 }
360