Java - 死鎖

/*
	死鎖就是兩個線程都被掛起，在等待區。程序終結
	
	線程1，實現的任務，先打開鎖1，再打開鎖2
	線程2，實現的任務，先打開鎖2，再打開鎖1
	線程1進入鎖1，CPU切換線程2，線程2進入鎖2；掛起等待。CPU切換線程1，掛起等待。

	線程1，實現的任務，先打開鎖1，再打開鎖2，打開鎖2，再打開鎖1，
	線程2，實現的任務，先打開鎖1，再打開鎖2，打開鎖2，再打開鎖1，
	線程1進入鎖2，CPU切換線程2，線程2進入鎖1；掛起等待。CPU切換線程1，掛起等待。

*/
class ThreadDemo 
{
	public static void main(String[] args) 
	{
		//die1 die1Run = new die1();
		die2 die2Run = new die2();
		//new Thread(die1Run,"d1").start();
		//die1Run.flag=false;
		//new Thread(die1Run,"d2").start();
		new Thread(die2Run,"d3").start();		
		new Thread(die2Run,"d4").start();		
		System.out.println("Hello World!");
	}
}
/*
class die1 implements Runnable
{
	private int num=20;
	boolean flag=true;	
	public void run(){
		if(flag){
			while(true)
			{
				synchronized(NewThread.class){				
					printNum();
				}
			}
		}else{
			while(true)
			{
				printNum();
			}
		}		
	}
	public synchronized void printNum(){		
		synchronized(NewThread.class){
			if(num>10){							
				System.out.println(num-- + "--" + Thread.currentThread().getName());				
			}
		}		
	}
}
*/
class die2 implements Runnable
{
	private int num=10;
	public void run(){
		while(true)
		{
			synchronized(NewThread.class){				
				printNum();
			}
			printNum();
		}		
	}
	public synchronized void printNum(){
		synchronized(NewThread.class){
			if(num>0){		
				for(int i=0;i<10000;i++){}
				System.out.println(num-- + "--" + Thread.currentThread().getName());				
			}
		}
	}
}