老师，关于可见性的问题

Question

我的代码并没有使用Volatile和Synchronized关键字保证可见性，为啥还是有可见性呢？？

public class SynchronizedClass {
    private int value = 100;

    public static void main(String[] args) throws InterruptedException {
        SynchronizedClass s = new SynchronizedClass();
        SynchronizedThread synchronizedThread = new SynchronizedThread(s);
        Thread t = new Thread(synchronizedThread);
        SynchronizedThread2 synchronizedThread2 = new SynchronizedThread2(s);
        Thread t2 = new Thread(synchronizedThread2);
        t.start();
        t2.start();
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }
}

class SynchronizedThread implements Runnable {
    private SynchronizedClass obj;

    public SynchronizedThread(SynchronizedClass obj) {
        this.obj = obj;
    }

    @Override
    public void run() {
        while (obj.getValue() == 100) {

        }
        System.out.println("end");
    }
}

class SynchronizedThread2 implements Runnable {
    private SynchronizedClass obj;

    public SynchronizedThread2(SynchronizedClass obj) {
        this.obj = obj;
    }

    @Override
    public void run() {
        obj.setValue(200);
        int i = 0;
        while (true) {
            i++;
        }
    }
}

Answer 1

悟空 2025-01-21 16:43:05

不使用关键字的时候，程序也会尽力，但是不保证能完全可见