- /*
- * @(#)AtomicInteger.java 1.5 04/01/12
- *
- * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- 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;
-
- /**
- * Create a new AtomicInteger with the given initial value.
- *
- * @param initialValue the initial value
- */
- public AtomicInteger(int initialValue) {
- value = initialValue;
- }
-
- /**
- * Create a new AtomicInteger with initial value <tt>0</tt>.
- */
- public AtomicInteger() {
- }
-
- /**
- * Get the current value.
- *
- * @return the current value
- */
- public final int get() {
- return value;
- }
-
- /**
- * Set to the given value.
- *
- * @param newValue the new value
- */
- public final void set(int newValue) {
- value = newValue;
- }
-
- /**
- * Set to the give value and return 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 set 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 set the value to the given updated value
- * if the current value <tt>==</tt> the expected value.
- * May fail spuriously.
- * @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 increment 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 decrement 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 add the given value to 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 increment 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 decrement 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 add the given value to 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();
- }
-
- }