concurrent/atomic/AtomicInteger.java

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0N/A * particular file as subject to the "Classpath" exception as provided
2362N/A * by Oracle in the LICENSE file that accompanied this code.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
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0N/A * You should have received a copy of the GNU General Public License version
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0N/A */
0N/A
0N/A/*
0N/A * This file is available under and governed by the GNU General Public
0N/A * License version 2 only, as published by the Free Software Foundation.
0N/A * However, the following notice accompanied the original version of this
0N/A * file:
0N/A *
0N/A * Written by Doug Lea with assistance from members of JCP JSR-166
0N/A * Expert Group and released to the public domain, as explained at
3984N/A * http://creativecommons.org/publicdomain/zero/1.0/
0N/A */
0N/A
0N/Apackage java.util.concurrent.atomic;
0N/Aimport sun.misc.Unsafe;
0N/A
0N/A/**
0N/A * An {@code int} value that may be updated atomically.  See the
0N/A * {@link java.util.concurrent.atomic} package specification for
0N/A * description of the properties of atomic variables. An
0N/A * {@code AtomicInteger} is used in applications such as atomically
0N/A * incremented counters, and cannot be used as a replacement for an
0N/A * {@link java.lang.Integer}. However, this class does extend
0N/A * {@code Number} to allow uniform access by tools and utilities that
0N/A * deal with numerically-based classes.
0N/A *
0N/A * @since 1.5
0N/A * @author Doug Lea
0N/A*/
0N/Apublic class AtomicInteger extends Number implements java.io.Serializable {
0N/A    private static final long serialVersionUID = 6214790243416807050L;
0N/A
0N/A    // setup to use Unsafe.compareAndSwapInt for updates
0N/A    private static final Unsafe unsafe = Unsafe.getUnsafe();
0N/A    private static final long valueOffset;
0N/A
0N/A    static {
0N/A      try {
0N/A        valueOffset = unsafe.objectFieldOffset
0N/A            (AtomicInteger.class.getDeclaredField("value"));
0N/A      } catch (Exception ex) { throw new Error(ex); }
0N/A    }
0N/A
0N/A    private volatile int value;
0N/A
0N/A    /**
0N/A     * Creates a new AtomicInteger with the given initial value.
0N/A     *
0N/A     * @param initialValue the initial value
0N/A     */
0N/A    public AtomicInteger(int initialValue) {
0N/A        value = initialValue;
0N/A    }
0N/A
0N/A    /**
0N/A     * Creates a new AtomicInteger with initial value {@code 0}.
0N/A     */
0N/A    public AtomicInteger() {
0N/A    }
0N/A
0N/A    /**
0N/A     * Gets the current value.
0N/A     *
0N/A     * @return the current value
0N/A     */
0N/A    public final int get() {
0N/A        return value;
0N/A    }
0N/A
0N/A    /**
0N/A     * Sets to the given value.
0N/A     *
0N/A     * @param newValue the new value
0N/A     */
0N/A    public final void set(int newValue) {
0N/A        value = newValue;
0N/A    }
0N/A
0N/A    /**
0N/A     * Eventually sets to the given value.
0N/A     *
0N/A     * @param newValue the new value
0N/A     * @since 1.6
0N/A     */
0N/A    public final void lazySet(int newValue) {
0N/A        unsafe.putOrderedInt(this, valueOffset, newValue);
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically sets to the given value and returns the old value.
0N/A     *
0N/A     * @param newValue the new value
0N/A     * @return the previous value
0N/A     */
0N/A    public final int getAndSet(int newValue) {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            if (compareAndSet(current, newValue))
0N/A                return current;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically sets the value to the given updated value
0N/A     * if the current value {@code ==} the expected value.
0N/A     *
0N/A     * @param expect the expected value
0N/A     * @param update the new value
0N/A     * @return true if successful. False return indicates that
0N/A     * the actual value was not equal to the expected value.
0N/A     */
0N/A    public final boolean compareAndSet(int expect, int update) {
0N/A        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically sets the value to the given updated value
0N/A     * if the current value {@code ==} the expected value.
0N/A     *
0N/A     * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
0N/A     * and does not provide ordering guarantees, so is only rarely an
0N/A     * appropriate alternative to {@code compareAndSet}.
0N/A     *
0N/A     * @param expect the expected value
0N/A     * @param update the new value
0N/A     * @return true if successful.
0N/A     */
0N/A    public final boolean weakCompareAndSet(int expect, int update) {
0N/A        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically increments by one the current value.
0N/A     *
0N/A     * @return the previous value
0N/A     */
0N/A    public final int getAndIncrement() {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current + 1;
0N/A            if (compareAndSet(current, next))
0N/A                return current;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically decrements by one the current value.
0N/A     *
0N/A     * @return the previous value
0N/A     */
0N/A    public final int getAndDecrement() {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current - 1;
0N/A            if (compareAndSet(current, next))
0N/A                return current;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically adds the given value to the current value.
0N/A     *
0N/A     * @param delta the value to add
0N/A     * @return the previous value
0N/A     */
0N/A    public final int getAndAdd(int delta) {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current + delta;
0N/A            if (compareAndSet(current, next))
0N/A                return current;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically increments by one the current value.
0N/A     *
0N/A     * @return the updated value
0N/A     */
0N/A    public final int incrementAndGet() {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current + 1;
0N/A            if (compareAndSet(current, next))
0N/A                return next;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically decrements by one the current value.
0N/A     *
0N/A     * @return the updated value
0N/A     */
0N/A    public final int decrementAndGet() {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current - 1;
0N/A            if (compareAndSet(current, next))
0N/A                return next;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Atomically adds the given value to the current value.
0N/A     *
0N/A     * @param delta the value to add
0N/A     * @return the updated value
0N/A     */
0N/A    public final int addAndGet(int delta) {
0N/A        for (;;) {
0N/A            int current = get();
0N/A            int next = current + delta;
0N/A            if (compareAndSet(current, next))
0N/A                return next;
0N/A        }
0N/A    }
0N/A
0N/A    /**
0N/A     * Returns the String representation of the current value.
0N/A     * @return the String representation of the current value.
0N/A     */
0N/A    public String toString() {
0N/A        return Integer.toString(get());
0N/A    }
0N/A
0N/A
0N/A    public int intValue() {
0N/A        return get();
0N/A    }
0N/A
0N/A    public long longValue() {
0N/A        return (long)get();
0N/A    }
0N/A
0N/A    public float floatValue() {
0N/A        return (float)get();
0N/A    }
0N/A
0N/A    public double doubleValue() {
0N/A        return (double)get();
0N/A    }
0N/A
0N/A}