并发变成-Volatile

一、以下代码会如何执行

public class test {

    public static void main(String [] args){
        ThreadDemo td = new ThreadDemo();
        new Thread(td).start();
        while(true){
            if(td.isFlag()){
                System.out.println("Thread end");
            }
        }

    }
}
class ThreadDemo implements Runnable {
    private boolean  flag = false;
    @Override
    public void run() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        flag = true;
        System.out.println("ThreadDemo end");
    }

    public boolean isFlag(){
        return this.flag;
    }
}

结果为主线程死循环下去，因为子线程修改的字段未刷新到主存中，导致主线程对flag一直不可见，增加volatile后可即时获取到子线程的修改。

标签：Thread,ThreadDemo,并发,flag,td,Volatile,线程,变成,public
来源： https://blog.csdn.net/wangaz521/article/details/98965714