java线程的上锁

import java.io.*;
import java.lang.*;
import java.util.*;
public class hehe implements Runnable{
	Timer ti = new Timer();
public static void main(String args[]){
		hehe he = new hehe();
		Thread t1 = new Thread(he);
		Thread t2 = new Thread(he);
		t1.start();
		t2.start();
	}
	public void  run(){
		ti.add(Thread.currentThread().getName());
	}
}


public class Timer {
	private static int num = 0;
	public void add(String name){
		synchronized(this){
			num++;
			try{
				Thread.sleep(1);
			}catch(Exception e){
				return ;
			}
			System.out.println(name+" "+num);
		}
	}
}

或者是直接在方法名字的前面加上synchronized关键字