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Diffstat (limited to 'libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicInteger.java')
| -rw-r--r-- | libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicInteger.java | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicInteger.java b/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicInteger.java new file mode 100644 index 000000000..0f723f613 --- /dev/null +++ b/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicInteger.java @@ -0,0 +1,234 @@ +/* + * Written by Doug Lea with assistance from members of JCP JSR-166 + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/licenses/publicdomain + */ + +package java.util.concurrent.atomic; +import sun.misc.Unsafe; + +/** + * An <tt>int</tt> value that may be updated atomically. See the + * {@link java.util.concurrent.atomic} package specification for + * description of the properties of atomic variables. An + * <tt>AtomicInteger</tt> is used in applications such as atomically + * incremented counters, and cannot be used as a replacement for an + * {@link java.lang.Integer}. However, this class does extend + * <tt>Number</tt> to allow uniform access by tools and utilities that + * deal with numerically-based classes. + * + * @since 1.5 + * @author Doug Lea +*/ +public class AtomicInteger extends Number implements java.io.Serializable { + private static final long serialVersionUID = 6214790243416807050L; + + // setup to use Unsafe.compareAndSwapInt for updates + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private static final long valueOffset; + + static { + try { + valueOffset = unsafe.objectFieldOffset + (AtomicInteger.class.getDeclaredField("value")); + } catch (Exception ex) { throw new Error(ex); } + } + + private volatile int value; + + /** + * Creates a new AtomicInteger with the given initial value. + * + * @param initialValue the initial value + */ + public AtomicInteger(int initialValue) { + value = initialValue; + } + + /** + * Creates a new AtomicInteger with initial value <tt>0</tt>. + */ + public AtomicInteger() { + } + + /** + * Gets the current value. + * + * @return the current value + */ + public final int get() { + return value; + } + + /** + * Sets to the given value. + * + * @param newValue the new value + */ + public final void set(int newValue) { + value = newValue; + } + + /** + * Eventually sets to the given value. + * + * @param newValue the new value + * @since 1.6 + */ + public final void lazySet(int newValue) { + unsafe.putOrderedInt(this, valueOffset, newValue); + } + + /** + * Atomically sets to the given value and returns the old value. + * + * @param newValue the new value + * @return the previous value + */ + public final int getAndSet(int newValue) { + for (;;) { + int current = get(); + if (compareAndSet(current, newValue)) + return current; + } + } + + /** + * Atomically sets the value to the given updated value + * if the current value <tt>==</tt> the expected value. + * + * @param expect the expected value + * @param update the new value + * @return true if successful. False return indicates that + * the actual value was not equal to the expected value. + */ + public final boolean compareAndSet(int expect, int update) { + return unsafe.compareAndSwapInt(this, valueOffset, expect, update); + } + + /** + * Atomically sets the value to the given updated value + * if the current value <tt>==</tt> the expected value. + * May fail spuriously and does not provide ordering guarantees, + * so is only rarely an appropriate alternative to <tt>compareAndSet</tt>. + * + * @param expect the expected value + * @param update the new value + * @return true if successful. + */ + public final boolean weakCompareAndSet(int expect, int update) { + return unsafe.compareAndSwapInt(this, valueOffset, expect, update); + } + + /** + * Atomically increments by one the current value. + * + * @return the previous value + */ + public final int getAndIncrement() { + for (;;) { + int current = get(); + int next = current + 1; + if (compareAndSet(current, next)) + return current; + } + } + + /** + * Atomically decrements by one the current value. + * + * @return the previous value + */ + public final int getAndDecrement() { + for (;;) { + int current = get(); + int next = current - 1; + if (compareAndSet(current, next)) + return current; + } + } + + /** + * Atomically adds the given value to the current value. + * + * @param delta the value to add + * @return the previous value + */ + public final int getAndAdd(int delta) { + for (;;) { + int current = get(); + int next = current + delta; + if (compareAndSet(current, next)) + return current; + } + } + + /** + * Atomically increments by one the current value. + * + * @return the updated value + */ + public final int incrementAndGet() { + for (;;) { + int current = get(); + int next = current + 1; + if (compareAndSet(current, next)) + return next; + } + } + + /** + * Atomically decrements by one the current value. + * + * @return the updated value + */ + public final int decrementAndGet() { + for (;;) { + int current = get(); + int next = current - 1; + if (compareAndSet(current, next)) + return next; + } + } + + /** + * Atomically adds the given value to the current value. + * + * @param delta the value to add + * @return the updated value + */ + public final int addAndGet(int delta) { + for (;;) { + int current = get(); + int next = current + delta; + if (compareAndSet(current, next)) + return next; + } + } + + /** + * Returns the String representation of the current value. + * @return the String representation of the current value. + */ + public String toString() { + return Integer.toString(get()); + } + + + public int intValue() { + return get(); + } + + public long longValue() { + return (long)get(); + } + + public float floatValue() { + return (float)get(); + } + + public double doubleValue() { + return (double)get(); + } + +} |