synchronized 锁的原理

public class Demo {
    private static int count = 0;

    public static void inc() {
        synchronized (Demo.class) {
            try {
                Thread.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            count++;
        }
    }

    public static void main(String[] args)
            throws InterruptedException {
        for (int i = 0; i < 1000; i++) {
            new Thread(() -> Demo.inc()).start();
        }
        Thread.sleep(3000);
        System.out.println("运行结果" + count);
    }
}