<转载>--java多线程死锁例子 TestDeadLock.java

  多线程的东西看了有两三遍了,但是直到数据库这门专业课都学完了,印象还是不很深刻,在备考的时候死记硬背了一些事务啦、死锁啦、隔离级别之类的概念,跟多线程有点共通之处.
 
  最近在看马士兵的视频教程,加深理解.

  貌似java的多线程没有判断死锁的机制,数据库里面是会判断是否发生死锁的.下面这个例子里却是无止境地等待对方释放资源.

public class TestDeadLock implements Runnable {
	public int flag = 1;

	static Object o1 = new Object();

	static Object o2 = new Object();

	public static void main(String[] args) {
		TestDeadLock t1 = new TestDeadLock();
		TestDeadLock t2 = new TestDeadLock();
		t1.flag = 0;
		t2.flag = 1;
		Thread th1 = new Thread(t1);
		Thread th2 = new Thread(t2);
		th1.start();
		th2.start();
	}

	public void run() {
		System.out.println("flag:"+flag);
		if (flag == 1) {
			synchronized (o1) {
				try {
					Thread.sleep(500);
				} catch (Exception e) {

				}
				synchronized (o2) {
					System.out.println("th1");
				}
			}
		}

		if (flag == 0) {
			synchronized (o2) {
				try {
					Thread.sleep(500);
				} catch (Exception e) {

				}
				synchronized (o1) {
					System.out.println("th2");
				}

			}
		}
	}

}