1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
public class ThreadService {

	public static void print(String stringLock){
		synchronized (stringLock) {
			while(true){
				System.out.println("当前线程："+Thread.currentThread().getName());
				try{
					Thread.sleep(3000);
				}catch(Exception e){
					e.printStackTrace();
				}
			}
		}
	}
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
public class ThreadA extends Thread{
	
	private ThreadService ts;

	public ThreadA(ThreadService ts) {
		super();
		this.ts = ts;
	}
	
	public void run(){
		ts.print("stringLock");
	}
	

}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
public class ThreadB extends Thread{
	
	private ThreadService ts;

	public ThreadB(ThreadService ts) {
		super();
		this.ts = ts;
	}
	
	public void run(){
		ts.print("stringLock");
	}

}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
//String类型的字符串作为锁对象造成死锁
//常量池的原因：String a = "1";String b = "1";a==b==true;
public class TestStringLockCauseBug {
	
	
	public static void main(String[] args) {
		
		//这个例子会由于锁都是字符串stringLock，导致线程B一直拿不到资源，因为字符串stringLock是常量池共享的（同一个），所以String类型一般不作为锁对象（把锁换成其他类型就可以了，比如new Object()）
		ThreadService ts =  new ThreadService();
		ThreadA a = new ThreadA(ts);
		a.setName("A");
		a.start();
		
		ThreadB b = new ThreadB(ts);
		b.setName("B");
		b.start();
	}

}