How to print non repeating element by two threads?

i want to print non repeating elements from the same resource by two threads.

here in below code , am printing repeated elements

class TestSleepMethod1 extends Thread{  
    public void run(){  
        for(int i=1;i<5;i++){  
            try{Thread.sleep(500);}catch(InterruptedException e){System.out.println(e);}  
            System.out.println(i);  
        }  
    }

    public static void main(String args[]){  
        TestSleepMethod1 t1=new TestSleepMethod1();  
        TestSleepMethod1 t2=new TestSleepMethod1();  

        t1.start();  
        t2.start();  
    }  
}  

The output :

1 1 2 2 3 3 4 4 . I want, if one thread prints "1" other thread should not print "1" again instead it should print 2 . How to achieve this condition? Thanks.