示例代码
public class TestMain implements Runnable {
//格式化
SimpleDateFormat sim = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
@Override
public synchronized void run() {
Date satrtTime = new Date();
String time = sim.format(satrtTime);
System.out.println(time + ":【" + Thread.currentThread().getName() + "访问了方法】");
try {
//睡眠3秒
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Date endTime = new Date();
String time2 = sim.format(endTime);
System.out.println(time2 + ":【" + Thread.currentThread().getName() + "准备退出这个方法了】");
}
public static void main(String[] args) throws Exception {
//创建一个对象
TestMain testMain1 = new TestMain();
System.out.println("运行开始");
Thread thread1 = new Thread(testMain1);
Thread thread2 = new Thread(testMain1);
thread1.start();
thread2.start();
//让主线程做个等待,等线程一和线程二都执行完它才继续执行
thread1.join();
thread2.join();
System.out.println("运行结束");
}
}
运行结果:
总结
从运行结果可以看出,Thread-1线程等待着Thread-0线程执行结束后才执行,这是因为用的是对象锁,而对象是相同的,所以锁也是相同的,锁只有一把,所以线程Thread-1需要等待
线程Thread-0释放锁后,才能去尝试获取锁,获取到锁后才能进入方法。