synchronized(static XX)失效的例子

import java.awt.AWTException;
import java.awt.Robot;


public class TestThread1 implements Runnable {
	
	private static String name;
	
	public TestThread1(String name){
		this.name=name;
	}

	@Override
	public void run() {
		synchronized(name){
			for(int i=0;i<10;i++){
				try {
					Robot r = new Robot();
					r.delay(1000);
				} catch (AWTException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				System.out.println(Thread.currentThread().getName()+" "+name+i);
			}
		}
	}
	
	public static void main(String args[]){
		TestThread1 th1 = new TestThread1("A");
		Thread t1 = new Thread(th1);
		t1.start();

		TestThread1 th2 = new TestThread1("B");
		Thread t2 = new Thread(th2);
		t2.start();
		
/*		Robot r;
		try {
			r = new Robot();
			r.delay(2000);
		} catch (AWTException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		TestThread1.name="C";*/
		TestThread1 th3 = new TestThread1("D");
		Thread t3 = new Thread(th3);
		t3.start();
	}

}

 结果：

Thread-0 D0

Thread-1 D0

Thread-1 D1

Thread-0 D1

Thread-0 D2

Thread-1 D2

Thread-1 D3

Thread-0 D3

Thread-1 D4

Thread-0 D4

Thread-1 D5

Thread-0 D5

Thread-1 D6

Thread-0 D6

Thread-1 D7

Thread-0 D7

Thread-0 D8

Thread-1 D8

Thread-1 D9

Thread-0 D9

Thread-2 D0

Thread-2 D1

Thread-2 D2

Thread-2 D3

Thread-2 D4

Thread-2 D5

Thread-2 D6

Thread-2 D7

Thread-2 D8

Thread-2 D9

 

发现当改变线程中static 的变量值的线程开启介入时，synchronized(static XX)便失效。

而下面的情况则未见失效，很诡异。

import java.awt.AWTException;
import java.awt.Robot;


public class TestThread1 implements Runnable {
	
	private static String name;
	
	public TestThread1(String name){
		this.name=name;
	}

	@Override
	public void run() {
		synchronized(name){
			for(int i=0;i<10;i++){
				try {
					Robot r = new Robot();
					r.delay(1000);
				} catch (AWTException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				System.out.println(Thread.currentThread().getName()+" "+name+i);
			}
		}
	}
	
	public static void main(String args[]){
		TestThread1 th1 = new TestThread1("A");
		Thread t1 = new Thread(th1);
		t1.start();

		TestThread1 th2 = new TestThread1("B");
		Thread t2 = new Thread(th2);
		t2.start();
		

	}

}

 结果：

Thread-0 B0

Thread-0 B1

Thread-0 B2

Thread-0 B3

Thread-0 B4

Thread-0 B5

Thread-0 B6

Thread-0 B7

Thread-0 B8

Thread-0 B9

Thread-1 B0

Thread-1 B1

Thread-1 B2

Thread-1 B3

Thread-1 B4

Thread-1 B5

Thread-1 B6

Thread-1 B7

Thread-1 B8

Thread-1 B9