同步锁 synchronized

package ba;

public class Tongbu implements Runnable{
	int i=100;
	
	public void run(){
		while(true){
			sell();
		}
	}
	
	public synchronized void sell(){
		if(i>0){
			System.out.println(Thread.currentThread().getName()+":"+i);
			i--;
		}
	}

}