Java Thread join,yield 区别

/**
 *
 *
 * @author William
 * @date Mar 15, 2013
 * @version 1.0
 */

public class GetStaticVal extends Thread{
	String id;
	public GetStaticVal(String id){
		this.id=id;
	}
	
	
	public void run()
	{
		if(id.equals("1")){
			for(int i=0;i<100000000;i++){
				StaticClass.val=i;
				//System.out.println(StaticClass.val);	
			}
			System.out.println(id+"==="+StaticClass.val);
		}else{
			System.out.println(id+"==="+StaticClass.val);	
		}
		
		
	}
	public static void main(String[] args) {

		
		GetStaticVal th1=new GetStaticVal("1");
		GetStaticVal th2=new GetStaticVal("2");
		GetStaticVal th3=new GetStaticVal("3");
		GetStaticVal th4=new GetStaticVal("4");
		System.out.println("begin="+StaticClass.val);
		
		th1.start();
		
		th1.yield(); //yield是先将自已执行权先暂时转让给别的线程,等别的线程都执行完再接着再执行
		
		//				try {
		//					th1.join(); //所以有线程同步后，要待到自已线程执行完再，执行其它线程
		//				} catch (InterruptedException e) {
		//					// TODO Auto-generated catch block
		//					e.printStackTrace();
		//				}
		
		th2.start();
		th3.start();
		th4.start();
		System.out.println("End="+StaticClass.val);
		
	}

}

 

 //Static Class

public class StaticClass {
	
	public static int val;

}