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.VarHandle;
39 import java.util.function.IntBinaryOperator;
40 import java.util.function.IntUnaryOperator;
41
42 /**
43 * An {@code int} value that may be updated atomically. See the
44 * {@link VarHandle} specification for descriptions of the properties
45 * of atomic accesses. An {@code AtomicInteger} is used in
46 * applications such as atomically incremented counters, and cannot be
47 * used as a replacement for an {@link java.lang.Integer}. However,
48 * this class does extend {@code Number} to allow uniform access by
49 * tools and utilities that deal with numerically-based classes.
50 *
51 * @since 1.5
52 * @author Doug Lea
53 */
54 public class AtomicInteger extends Number implements java.io.Serializable {
55 private static final long serialVersionUID = 6214790243416807050L;
56
57 /*
58 * This class intended to be implemented using VarHandles, but there
59 * are unresolved cyclic startup dependencies.
60 */
61 private static final jdk.internal.misc.Unsafe U = jdk.internal.misc.Unsafe.getUnsafe();
62 private static final long VALUE = U.objectFieldOffset(AtomicInteger.class, "value");
63
64 private volatile int value;
65
66 /**
67 * Creates a new AtomicInteger with the given initial value.
68 *
69 * @param initialValue the initial value
70 */
71 public AtomicInteger(int initialValue) {
72 value = initialValue;
73 }
74
75 /**
76 * Creates a new AtomicInteger with initial value {@code 0}.
77 */
78 public AtomicInteger() {
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 int get() {
88 return value;
89 }
90
91 /**
92 * Sets the value to {@code newValue},
93 * with memory effects as specified by {@link VarHandle#setVolatile}.
94 *
95 * @param newValue the new value
96 */
97 public final void set(int newValue) {
98 value = newValue;
99 }
100
101 /**
102 * Sets the value to {@code newValue},
103 * with memory effects as specified by {@link VarHandle#setRelease}.
104 *
105 * @param newValue the new value
106 * @since 1.6
107 */
108 public final void lazySet(int newValue) {
109 U.putIntRelease(this, VALUE, newValue);
110 }
111
112 /**
113 * Atomically sets the value to {@code newValue} and returns the old value,
114 * with memory effects as specified by {@link VarHandle#getAndSet}.
115 *
116 * @param newValue the new value
117 * @return the previous value
118 */
119 public final int getAndSet(int newValue) {
120 return U.getAndSetInt(this, VALUE, newValue);
121 }
122
123 /**
124 * Atomically sets the value to {@code newValue}
125 * if the current value {@code == expectedValue},
126 * with memory effects as specified by {@link VarHandle#compareAndSet}.
127 *
128 * @param expectedValue the expected value
129 * @param newValue the new value
130 * @return {@code true} if successful. False return indicates that
131 * the actual value was not equal to the expected value.
132 */
133 public final boolean compareAndSet(int expectedValue, int newValue) {
134 return U.compareAndSetInt(this, VALUE, expectedValue, newValue);
135 }
136
137 /**
138 * Possibly atomically sets the value to {@code newValue}
139 * if the current value {@code == expectedValue},
140 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
141 *
142 * @deprecated This method has plain memory effects but the method
143 * name implies volatile memory effects (see methods such as
144 * {@link #compareAndExchange} and {@link #compareAndSet}). To avoid
145 * confusion over plain or volatile memory effects it is recommended that
146 * the method {@link #weakCompareAndSetPlain} be used instead.
147 *
148 * @param expectedValue the expected value
149 * @param newValue the new value
150 * @return {@code true} if successful
151 * @see #weakCompareAndSetPlain
152 */
153 @Deprecated(since="9")
154 public final boolean weakCompareAndSet(int expectedValue, int newValue) {
155 return U.weakCompareAndSetIntPlain(this, VALUE, expectedValue, newValue);
156 }
157
158 /**
159 * Possibly atomically sets the value to {@code newValue}
160 * if the current value {@code == expectedValue},
161 * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.
162 *
163 * @param expectedValue the expected value
164 * @param newValue the new value
165 * @return {@code true} if successful
166 * @since 9
167 */
168 public final boolean weakCompareAndSetPlain(int expectedValue, int newValue) {
169 return U.weakCompareAndSetIntPlain(this, VALUE, expectedValue, newValue);
170 }
171
172 /**
173 * Atomically increments the current value,
174 * with memory effects as specified by {@link VarHandle#getAndAdd}.
175 *
176 * <p>Equivalent to {@code getAndAdd(1)}.
177 *
178 * @return the previous value
179 */
180 public final int getAndIncrement() {
181 return U.getAndAddInt(this, VALUE, 1);
182 }
183
184 /**
185 * Atomically decrements the current value,
186 * with memory effects as specified by {@link VarHandle#getAndAdd}.
187 *
188 * <p>Equivalent to {@code getAndAdd(-1)}.
189 *
190 * @return the previous value
191 */
192 public final int getAndDecrement() {
193 return U.getAndAddInt(this, VALUE, -1);
194 }
195
196 /**
197 * Atomically adds the given value to the current value,
198 * with memory effects as specified by {@link VarHandle#getAndAdd}.
199 *
200 * @param delta the value to add
201 * @return the previous value
202 */
203 public final int getAndAdd(int delta) {
204 return U.getAndAddInt(this, VALUE, delta);
205 }
206
207 /**
208 * Atomically increments the current value,
209 * with memory effects as specified by {@link VarHandle#getAndAdd}.
210 *
211 * <p>Equivalent to {@code addAndGet(1)}.
212 *
213 * @return the updated value
214 */
215 public final int incrementAndGet() {
216 return U.getAndAddInt(this, VALUE, 1) + 1;
217 }
218
219 /**
220 * Atomically decrements the current value,
221 * with memory effects as specified by {@link VarHandle#getAndAdd}.
222 *
223 * <p>Equivalent to {@code addAndGet(-1)}.
224 *
225 * @return the updated value
226 */
227 public final int decrementAndGet() {
228 return U.getAndAddInt(this, VALUE, -1) - 1;
229 }
230
231 /**
232 * Atomically adds the given value to the current value,
233 * with memory effects as specified by {@link VarHandle#getAndAdd}.
234 *
235 * @param delta the value to add
236 * @return the updated value
237 */
238 public final int addAndGet(int delta) {
239 return U.getAndAddInt(this, VALUE, delta) + delta;
240 }
241
242 /**
243 * Atomically updates the current value with the results of
244 * applying the given function, returning the previous value. The
245 * function should be side-effect-free, since it may be re-applied
246 * when attempted updates fail due to contention among threads.
247 *
248 * @param updateFunction a side-effect-free function
249 * @return the previous value
250 * @since 1.8
251 */
252 public final int getAndUpdate(IntUnaryOperator updateFunction) {
253 int prev = get(), next = 0;
254 for (boolean haveNext = false;;) {
255 if (!haveNext)
256 next = updateFunction.applyAsInt(prev);
257 if (weakCompareAndSetVolatile(prev, next))
258 return prev;
259 haveNext = (prev == (prev = get()));
260 }
261 }
262
263 /**
264 * Atomically updates the current value with the results of
265 * applying the given function, returning the updated value. The
266 * function should be side-effect-free, since it may be re-applied
267 * when attempted updates fail due to contention among threads.
268 *
269 * @param updateFunction a side-effect-free function
270 * @return the updated value
271 * @since 1.8
272 */
273 public final int updateAndGet(IntUnaryOperator updateFunction) {
274 int prev = get(), next = 0;
275 for (boolean haveNext = false;;) {
276 if (!haveNext)
277 next = updateFunction.applyAsInt(prev);
278 if (weakCompareAndSetVolatile(prev, next))
279 return next;
280 haveNext = (prev == (prev = get()));
281 }
282 }
283
284 /**
285 * Atomically updates the current value with the results of
286 * applying the given function to the current and given values,
287 * returning the previous value. The function should be
288 * side-effect-free, since it may be re-applied when attempted
289 * updates fail due to contention among threads. The function
290 * is applied with the current value as its first argument,
291 * and the given update as the second argument.
292 *
293 * @param x the update value
294 * @param accumulatorFunction a side-effect-free function of two arguments
295 * @return the previous value
296 * @since 1.8
297 */
298 public final int getAndAccumulate(int x,
299 IntBinaryOperator accumulatorFunction) {
300 int prev = get(), next = 0;
301 for (boolean haveNext = false;;) {
302 if (!haveNext)
303 next = accumulatorFunction.applyAsInt(prev, x);
304 if (weakCompareAndSetVolatile(prev, next))
305 return prev;
306 haveNext = (prev == (prev = get()));
307 }
308 }
309
310 /**
311 * Atomically updates the current value with the results of
312 * applying the given function to the current and given values,
313 * returning the updated value. The function should be
314 * side-effect-free, since it may be re-applied when attempted
315 * updates fail due to contention among threads. The function
316 * is applied with the current value as its first argument,
317 * and the given update as the second argument.
318 *
319 * @param x the update value
320 * @param accumulatorFunction a side-effect-free function of two arguments
321 * @return the updated value
322 * @since 1.8
323 */
324 public final int accumulateAndGet(int x,
325 IntBinaryOperator accumulatorFunction) {
326 int prev = get(), next = 0;
327 for (boolean haveNext = false;;) {
328 if (!haveNext)
329 next = accumulatorFunction.applyAsInt(prev, x);
330 if (weakCompareAndSetVolatile(prev, next))
331 return next;
332 haveNext = (prev == (prev = get()));
333 }
334 }
335
336 /**
337 * Returns the String representation of the current value.
338 * @return the String representation of the current value
339 */
340 public String toString() {
341 return Integer.toString(get());
342 }
343
344 /**
345 * Returns the current value of this {@code AtomicInteger} as an
346 * {@code int},
347 * with memory effects as specified by {@link VarHandle#getVolatile}.
348 *
349 * Equivalent to {@link #get()}.
350 */
351 public int intValue() {
352 return get();
353 }
354
355 /**
356 * Returns the current value of this {@code AtomicInteger} as a
357 * {@code long} after a widening primitive conversion,
358 * with memory effects as specified by {@link VarHandle#getVolatile}.
359 * @jls 5.1.2 Widening Primitive Conversions
360 */
361 public long longValue() {
362 return (long)get();
363 }
364
365 /**
366 * Returns the current value of this {@code AtomicInteger} as a
367 * {@code float} after a widening primitive conversion,
368 * with memory effects as specified by {@link VarHandle#getVolatile}.
369 * @jls 5.1.2 Widening Primitive Conversions
370 */
371 public float floatValue() {
372 return (float)get();
373 }
374
375 /**
376 * Returns the current value of this {@code AtomicInteger} as a
377 * {@code double} after a widening primitive conversion,
378 * with memory effects as specified by {@link VarHandle#getVolatile}.
379 * @jls 5.1.2 Widening Primitive Conversions
380 */
381 public double doubleValue() {
382 return (double)get();
383 }
384
385 // jdk9
386
387 /**
388 * Returns the current value, with memory semantics of reading as
389 * if the variable was declared non-{@code volatile}.
390 *
391 * @return the value
392 * @since 9
393 */
394 public final int getPlain() {
395 return U.getInt(this, VALUE);
396 }
397
398 /**
399 * Sets the value to {@code newValue}, with memory semantics
400 * of setting as if the variable was declared non-{@code volatile}
401 * and non-{@code final}.
402 *
403 * @param newValue the new value
404 * @since 9
405 */
406 public final void setPlain(int newValue) {
407 U.putInt(this, VALUE, newValue);
408 }
409
410 /**
411 * Returns the current value,
412 * with memory effects as specified by {@link VarHandle#getOpaque}.
413 *
414 * @return the value
415 * @since 9
416 */
417 public final int getOpaque() {
418 return U.getIntOpaque(this, VALUE);
419 }
420
421 /**
422 * Sets the value to {@code newValue},
423 * with memory effects as specified by {@link VarHandle#setOpaque}.
424 *
425 * @param newValue the new value
426 * @since 9
427 */
428 public final void setOpaque(int newValue) {
429 U.putIntOpaque(this, VALUE, newValue);
430 }
431
432 /**
433 * Returns the current value,
434 * with memory effects as specified by {@link VarHandle#getAcquire}.
435 *
436 * @return the value
437 * @since 9
438 */
439 public final int getAcquire() {
440 return U.getIntAcquire(this, VALUE);
441 }
442
443 /**
444 * Sets the value to {@code newValue},
445 * with memory effects as specified by {@link VarHandle#setRelease}.
446 *
447 * @param newValue the new value
448 * @since 9
449 */
450 public final void setRelease(int newValue) {
451 U.putIntRelease(this, VALUE, newValue);
452 }
453
454 /**
455 * Atomically sets the value to {@code newValue} if the current value,
456 * referred to as the <em>witness value</em>, {@code == expectedValue},
457 * with memory effects as specified by
458 * {@link VarHandle#compareAndExchange}.
459 *
460 * @param expectedValue the expected value
461 * @param newValue the new value
462 * @return the witness value, which will be the same as the
463 * expected value if successful
464 * @since 9
465 */
466 public final int compareAndExchange(int expectedValue, int newValue) {
467 return U.compareAndExchangeInt(this, VALUE, expectedValue, newValue);
468 }
469
470 /**
471 * Atomically sets the value to {@code newValue} if the current value,
472 * referred to as the <em>witness value</em>, {@code == expectedValue},
473 * with memory effects as specified by
474 * {@link VarHandle#compareAndExchangeAcquire}.
475 *
476 * @param expectedValue the expected value
477 * @param newValue the new value
478 * @return the witness value, which will be the same as the
479 * expected value if successful
480 * @since 9
481 */
482 public final int compareAndExchangeAcquire(int expectedValue, int newValue) {
483 return U.compareAndExchangeIntAcquire(this, VALUE, expectedValue, newValue);
484 }
485
486 /**
487 * Atomically sets the value to {@code newValue} if the current value,
488 * referred to as the <em>witness value</em>, {@code == expectedValue},
489 * with memory effects as specified by
490 * {@link VarHandle#compareAndExchangeRelease}.
491 *
492 * @param expectedValue the expected value
493 * @param newValue the new value
494 * @return the witness value, which will be the same as the
495 * expected value if successful
496 * @since 9
497 */
498 public final int compareAndExchangeRelease(int expectedValue, int newValue) {
499 return U.compareAndExchangeIntRelease(this, VALUE, expectedValue, newValue);
500 }
501
502 /**
503 * Possibly atomically sets the value to {@code newValue} if
504 * the current value {@code == expectedValue},
505 * with memory effects as specified by
506 * {@link VarHandle#weakCompareAndSet}.
507 *
508 * @param expectedValue the expected value
509 * @param newValue the new value
510 * @return {@code true} if successful
511 * @since 9
512 */
513 public final boolean weakCompareAndSetVolatile(int expectedValue, int newValue) {
514 return U.weakCompareAndSetInt(this, VALUE, expectedValue, newValue);
515 }
516
517 /**
518 * Possibly atomically sets the value to {@code newValue} if
519 * the current value {@code == expectedValue},
520 * with memory effects as specified by
521 * {@link VarHandle#weakCompareAndSetAcquire}.
522 *
523 * @param expectedValue the expected value
524 * @param newValue the new value
525 * @return {@code true} if successful
526 * @since 9
527 */
528 public final boolean weakCompareAndSetAcquire(int expectedValue, int newValue) {
529 return U.weakCompareAndSetIntAcquire(this, VALUE, expectedValue, newValue);
530 }
531
532 /**
533 * Possibly atomically sets the value to {@code newValue} if
534 * the current value {@code == expectedValue},
535 * with memory effects as specified by
536 * {@link VarHandle#weakCompareAndSetRelease}.
537 *
538 * @param expectedValue the expected value
539 * @param newValue the new value
540 * @return {@code true} if successful
541 * @since 9
542 */
543 public final boolean weakCompareAndSetRelease(int expectedValue, int newValue) {
544 return U.weakCompareAndSetIntRelease(this, VALUE, expectedValue, newValue);
545 }
546
547 }