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 if (initialValue)
72 value = 1;
73 }
74
75 /**
76 * Creates a new {@code AtomicBoolean} with initial value {@code false}.
77 */
78 public AtomicBoolean() {
79 }
80
81 /**
82 * Returns the current value,
83 * with memory effects as specified by {@link VarHandle#getVolatile}.
84 *
85 * @return the current value
86 */
87 public final boolean get() {
88 return value != 0;
89 }
90
91 /**
92 * Atomically sets the value to {@code newValue}
93 * if the current value {@code == expectedValue},
94 * with memory effects as specified by {@link VarHandle#compareAndSet}.
95 *
96 * @param expectedValue the expected value
97 * @param newValue the new value
98 * @return {@code true} if successful. False return indicates that
99 * the actual value was not equal to the expected value.
100 */
101 public final boolean compareAndSet(boolean expectedValue, boolean newValue) {
102 return VALUE.compareAndSet(this,
103 (expectedValue ? 1 : 0),
104 (newValue ? 1 : 0));
105 }
106
107 /**
108 * Possibly atomically sets the value to {@code newValue}
109 * if the current value {@code == expectedValue},
110 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
111 *
112 * @deprecated This method has plain memory effects but the method
113 * name implies volatile memory effects (see methods such as
114 * {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
115 * confusion over plain or volatile memory effects it is recommended that
116 * the method {@link #weakCompareAndSetPlain} be used instead.
117 *
118 * @param expectedValue the expected value
119 * @param newValue the new value
120 * @return {@code true} if successful
121 * @see #weakCompareAndSetPlain
122 */
123 @Deprecated(since="9")
124 public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {
125 return VALUE.weakCompareAndSetPlain(this,
126 (expectedValue ? 1 : 0),
127 (newValue ? 1 : 0));
128 }
129
130 /**
131 * Possibly atomically sets the value to {@code newValue}
132 * if the current value {@code == expectedValue},
133 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
134 *
135 * @param expectedValue the expected value
136 * @param newValue the new value
137 * @return {@code true} if successful
138 * @since 9
139 */
140 public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {
141 return VALUE.weakCompareAndSetPlain(this,
142 (expectedValue ? 1 : 0),
143 (newValue ? 1 : 0));
144 }
145
146 /**
147 * Sets the value to {@code newValue},
148 * with memory effects as specified by {@link VarHandle#setVolatile}.
149 *
150 * @param newValue the new value
151 */
152 public final void set(boolean newValue) {
153 value = newValue ? 1 : 0;
154 }
155
156 /**
157 * Sets the value to {@code newValue},
158 * with memory effects as specified by {@link VarHandle#setRelease}.
159 *
160 * @param newValue the new value
161 * @since 1.6
162 */
163 public final void lazySet(boolean newValue) {
164 VALUE.setRelease(this, (newValue ? 1 : 0));
165 }
166
167 /**
168 * Atomically sets the value to {@code newValue} and returns the old value,
169 * with memory effects as specified by {@link VarHandle#getAndSet}.
170 *
171 * @param newValue the new value
172 * @return the previous value
173 */
174 public final boolean getAndSet(boolean newValue) {
175 return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;
176 }
177
178 /**
179 * Returns the String representation of the current value.
180 * @return the String representation of the current value
181 */
182 public String toString() {
183 return Boolean.toString(get());
184 }
185
186 // jdk9
187
188 /**
189 * Returns the current value, with memory semantics of reading as
190 * if the variable was declared non-{@code volatile}.
191 *
192 * @return the value
193 * @since 9
194 */
195 public final boolean getPlain() {
196 return (int)VALUE.get(this) != 0;
197 }
198
199 /**
200 * Sets the value to {@code newValue}, with memory semantics
201 * of setting as if the variable was declared non-{@code volatile}
202 * and non-{@code final}.
203 *
204 * @param newValue the new value
205 * @since 9
206 */
207 public final void setPlain(boolean newValue) {
208 VALUE.set(this, newValue ? 1 : 0);
209 }
210
211 /**
212 * Returns the current value,
213 * with memory effects as specified by {@link VarHandle#getOpaque}.
214 *
215 * @return the value
216 * @since 9
217 */
218 public final boolean getOpaque() {
219 return (int)VALUE.getOpaque(this) != 0;
220 }
221
222 /**
223 * Sets the value to {@code newValue},
224 * with memory effects as specified by {@link VarHandle#setOpaque}.
225 *
226 * @param newValue the new value
227 * @since 9
228 */
229 public final void setOpaque(boolean newValue) {
230 VALUE.setOpaque(this, newValue ? 1 : 0);
231 }
232
233 /**
234 * Returns the current value,
235 * with memory effects as specified by {@link VarHandle#getAcquire}.
236 *
237 * @return the value
238 * @since 9
239 */
240 public final boolean getAcquire() {
241 return (int)VALUE.getAcquire(this) != 0;
242 }
243
244 /**
245 * Sets the value to {@code newValue},
246 * with memory effects as specified by {@link VarHandle#setRelease}.
247 *
248 * @param newValue the new value
249 * @since 9
250 */
251 public final void setRelease(boolean newValue) {
252 VALUE.setRelease(this, newValue ? 1 : 0);
253 }
254
255 /**
256 * Atomically sets the value to {@code newValue} if the current value,
257 * referred to as the <em>witness value</em>, {@code == expectedValue},
258 * with memory effects as specified by
259 * {@link VarHandle#compareAndExchange}.
260 *
261 * @param expectedValue the expected value
262 * @param newValue the new value
263 * @return the witness value, which will be the same as the
264 * expected value if successful
265 * @since 9
266 */
267 public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {
268 return (int)VALUE.compareAndExchange(this,
269 (expectedValue ? 1 : 0),
270 (newValue ? 1 : 0)) != 0;
271 }
272
273 /**
274 * Atomically sets the value to {@code newValue} if the current value,
275 * referred to as the <em>witness value</em>, {@code == expectedValue},
276 * with memory effects as specified by
277 * {@link VarHandle#compareAndExchangeAcquire}.
278 *
279 * @param expectedValue the expected value
280 * @param newValue the new value
281 * @return the witness value, which will be the same as the
282 * expected value if successful
283 * @since 9
284 */
285 public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {
286 return (int)VALUE.compareAndExchangeAcquire(this,
287 (expectedValue ? 1 : 0),
288 (newValue ? 1 : 0)) != 0;
289 }
290
291 /**
292 * Atomically sets the value to {@code newValue} if the current value,
293 * referred to as the <em>witness value</em>, {@code == expectedValue},
294 * with memory effects as specified by
295 * {@link VarHandle#compareAndExchangeRelease}.
296 *
297 * @param expectedValue the expected value
298 * @param newValue the new value
299 * @return the witness value, which will be the same as the
300 * expected value if successful
301 * @since 9
302 */
303 public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {
304 return (int)VALUE.compareAndExchangeRelease(this,
305 (expectedValue ? 1 : 0),
306 (newValue ? 1 : 0)) != 0;
307 }
308
309 /**
310 * Possibly atomically sets the value to {@code newValue} if the current
311 * value {@code == expectedValue},
312 * with memory effects as specified by
313 * {@link VarHandle#weakCompareAndSet}.
314 *
315 * @param expectedValue the expected value
316 * @param newValue the new value
317 * @return {@code true} if successful
318 * @since 9
319 */
320 public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {
321 return VALUE.weakCompareAndSet(this,
322 (expectedValue ? 1 : 0),
323 (newValue ? 1 : 0));
324 }
325
326 /**
327 * Possibly atomically sets the value to {@code newValue} if the current
328 * value {@code == expectedValue},
329 * with memory effects as specified by
330 * {@link VarHandle#weakCompareAndSetAcquire}.
331 *
332 * @param expectedValue the expected value
333 * @param newValue the new value
334 * @return {@code true} if successful
335 * @since 9
336 */
337 public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {
338 return VALUE.weakCompareAndSetAcquire(this,
339 (expectedValue ? 1 : 0),
340 (newValue ? 1 : 0));
341 }
342
343 /**
344 * Possibly atomically sets the value to {@code newValue} if the current
345 * value {@code == expectedValue},
346 * with memory effects as specified by
347 * {@link VarHandle#weakCompareAndSetRelease}.
348 *
349 * @param expectedValue the expected value
350 * @param newValue the new value
351 * @return {@code true} if successful
352 * @since 9
353 */
354 public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {
355 return VALUE.weakCompareAndSetRelease(this,
356 (expectedValue ? 1 : 0),
357 (newValue ? 1 : 0));
358 }
359
360 }