3. 原子变量-CAS算法

1. 是什么 ？

2. CAS算法模拟

package com.gf.demo03;
public class TestCompareAndSwap {

	public static void main(String[] args) {
		CompareAndSwap cas = new CompareAndSwap();
		for (int i = 0; i < 10; i++) {
			new Thread(new Runnable() {

				@Override
				public void run() {
					int expectedValue = cas.get();
					boolean b = cas.compareAndSet(expectedValue, (int)(Math.random() * 101));
					System.out.println(b);
				}
			}).start();
		}
	}

}

class CompareAndSwap{
	private int value;

	//获取内存值
	public synchronized int get(){
		return value;
	}

	//比较
	public synchronized int compareAndSwap(int expectedValue,int newValue){
		int oldValue = value;
		if(oldValue == expectedValue){
			this.value = newValue;
		}

		return oldValue;
	}

	//设置
	public synchronized boolean compareAndSet(int expectedValue,int newValue){
		return expectedValue == compareAndSwap(expectedValue, newValue);
	}
}

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