Java多线程深入学习-atomic原子类实现-AtomicInteger源码分析

/**
 * AtomicInteger 原子Integer操作类 继承Number抽象类
 */
public class AtomicInteger extends Number implements java.io.Serializable {
    private static final long serialVersionUID = 6214790243416807050L;

    /**
     * 引入Unsafe类 并获取value在对象重的内存地址偏移量
     */
    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); }
    }
    /** 定义int的value */
    private volatile int value;

    /** 构造方法 */
    public AtomicInteger(int initialValue) {
        value = initialValue;
    }
    public AtomicInteger() {
    }
    public final int get() {
        return value;
    }
    public final void set(int newValue) {
        value = newValue;
    }
    
    /**
     * 利用unsafe类操作实现原子操作
     */
    public final void lazySet(int newValue) {
        unsafe.putOrderedInt(this, valueOffset, newValue);
    }
    public final int getAndSet(int newValue) {
        return unsafe.getAndSetInt(this, valueOffset, newValue);
    }
    /**
     * 比较并赋值
     */
    public final boolean compareAndSet(int expect, int update) {
        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
    }
    public final boolean weakCompareAndSet(int expect, int update) {
        return unsafe.compareAndSwapInt(this, valueOffset, expect, update);
    }
    /**
     * +1与-1的原子操作 返回操作前的值
     */
    public final int getAndIncrement() {
        return unsafe.getAndAddInt(this, valueOffset, 1);	//操作直到完成
    }
    public final int getAndDecrement() {
        return unsafe.getAndAddInt(this, valueOffset, -1);	//操作直到完成
    }

    /**
     * 添加指定值 并返添加前的值
     */
    public final int getAndAdd(int delta) {
        return unsafe.getAndAddInt(this, valueOffset, delta);	//操作直到完成
    }
    /**
     * 同上操作  返回操作后的值
     */
    public final int incrementAndGet() {
        return unsafe.getAndAddInt(this, valueOffset, 1) + 1;	//操作直到完成
    }
    public final int decrementAndGet() {
        return unsafe.getAndAddInt(this, valueOffset, -1) - 1;	//操作直到完成
    }
    public final int addAndGet(int delta) {
        return unsafe.getAndAddInt(this, valueOffset, delta) + delta;
    }

    /** 根据传入的函数式接口对值进行操作 */
    public final int getAndUpdate(IntUnaryOperator updateFunction) {
        int prev, next;
        do {
            prev = get();
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSet(prev, next));	//循环操作直到操作成功
        return prev;
    }
    public final int updateAndGet(IntUnaryOperator updateFunction) {
        int prev, next;
        do {
            prev = get();
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSet(prev, next));//循环操作直到操作成功
        return next;
    }
    public final int getAndAccumulate(int x, IntBinaryOperator accumulatorFunction) {
        int prev, next;
        do {
            prev = get();
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSet(prev, next));//循环操作直到操作成功
        return prev;
    }
    public final int accumulateAndGet(int x, IntBinaryOperator accumulatorFunction) {
        int prev, next;
        do {
            prev = get();
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSet(prev, next));//循环操作直到操作成功
        return next;
    }

    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();
    }
}