一个关于Java多线程的问题

Question

请问为什么会出现这样的执行结果？两个线程同时执行，同时拿到了count = 8我能理解，但如果两个线程都执行了count++，为什么结果不是10？难道是 count = count + 1，两者都拿到了 8，+1之后两者又都更新为9，这整个执行过程中有什么细节吗？这个静态变量在多线程中有什么说法？

public class Test02 implements Runnable {
    private static int count;

    public Test02() {
        count = 0;
    }

    public void run() {
        synchronized (this) {
            for (int i = 0; i < 5; i++) {
                try {
                    System.out.println(Thread.currentThread().getName() + ":" + (count++));
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    
    public int getCount() {
        return count;
    }

    public static void main(String[] args) {
        Thread thread1 = new Thread(new Test02(), "SyncThread1");
        Thread thread2 = new Thread(new Test02(), "SyncThread2");
        thread1.start();
        thread2.start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(test02.getCount());
    }
}

Answer 1

用互斥锁