Java中的原子类AtomicInteger使用详解

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerDemo {
    public static void main(String[] args) throws InterruptedException {
        test1();
        test2();
    }
    private static void test1() throws InterruptedException {
        Counter counter = new Counter();
        for (int i = 0; i < 10; i++) {
            new Thread(()->{
                for (int j = 0; j < 1000; j++) {
                    counter.addCount();
                }
            }).start();
        }
        Thread.sleep(1000);
        System.out.println("test1 count = " + counter.getCount());
    }
    private static void test2() throws InterruptedException {
        AtomicInteger count = new AtomicInteger();
        for (int i = 0; i < 10; i++) {
            new Thread(()->{
                for (int j = 0; j < 1000; j++) {
                    count.incrementAndGet();
                }
            }).start();
        }
        Thread.sleep(1000);
        System.out.println("test2 count = " + count.get());
    }
}
public class Counter {
    private volatile static int count = 0;
    public void addCount(){
        count++;
    }
    public int getCount(){
        return count;
    }
}

public class AtomicInteger extends Number implements java.io.Serializable

    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;

    public AtomicInteger(int initialValue) {
        value = initialValue;
    }
    public AtomicInteger() {
    }

    public final int incrementAndGet() {
        return unsafe.getAndAddInt(this, valueOffset, 1) + 1;
    }

    public final int getAndAddInt(Object var1, long var2, int var4) {
        int var5;
        do {
            var5 = this.getIntVolatile(var1, var2);
        } while(!this.compareAndSwapInt(var1, var2, var5, var5 + var4));

        return var5;
    }