普通变量升级为原子功能

AtomicIntegerFieldUpdater 对普通变量进行升级
使用场景：偶尔需要一个原子get-set操作
注意点：：
可见范围
不支持修改static类型的变量

public class AtomicIntegerFieldUpdaterDemo implements Runnable{
     static Candidate tom;
     static Candidate peter;
    // 对包装成原子类的变量不能添加static
    public static class Candidate{
        volatile int score;
    }
    public static AtomicIntegerFieldUpdater<Candidate> scoreUpdater = AtomicIntegerFieldUpdater.newUpdater(Candidate.class,"score");
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            peter.score++;
            scoreUpdater.getAndIncrement(tom);
        }
    }
    public static void main(String[] args) throws InterruptedException {
        tom = new Candidate();
        peter = new Candidate();
        AtomicIntegerFieldUpdaterDemo r = new AtomicIntegerFieldUpdaterDemo();
        Thread t1 = new Thread(r);
        Thread t2 = new Thread(r);
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println(peter.score);
        System.out.println(tom.score);
    }
}