一、主线程等待法#

        package mythread;  

        public class MyThread extends Thread  
          {  
             private String value1;  
             private String value2;  

        public void run()  
          {  
             value1 = "有数据了";  
              value2 = "有数据了";  
           }  
public static void main(String[] args) throws Exception  
       {  
          MyThread thread = new MyThread();  
          thread.start(); 
          while (thread.value1 == null || thread.value2 == null)sleep(100); 
          System.out.println("value1:" + thread.value1);  
          System.out.println("value2:" + thread.value2);  
       }   
}  

此方法就是让主现成空转，等待数据，耗费系统资源。

一、Thread join()方法，系统自动等待线程完成后再执行#

  class ThreadA implements Runnable {  
     private int counter;  

    @Override  
        public void run() {  
            while (counter <= 10) {  
              System.out.print("Counter = " + counter + " ");  
                counter++;  
        }  
          System.out.println();  
    }  
}  

class ThreadB implements Runnable {  

  private int i;  

  @Override  
    public void run() {  
        while (i <= 10) {  
          System.out.print("i = " + i + " ");  
            i++;  
        }  
        System.out.println();  
    }  
}  

public class ThreadTester {  
public static void main(String[] args) throws InterruptedException {  
    Thread t1 = new Thread(new ThreadA());  
    Thread t2 = new Thread(new ThreadB());  
    t1.start();  
    t1.join(); // wait t1 to be finished  
    t2.start();  
    t2.join(); // in this program, this may be removed  
  }  
}

三、利用线程池，实现Callable接口

public class Test { 
public static void main(String[] args) throws ExecutionException, InterruptedException { 
//创建一个线程池 
ExecutorService pool = Executors.newFixedThreadPool(2); 
//创建两个有返回值的任务 
Callable c1 = new MyCallable("A"); 
Callable c2 = new MyCallable("B"); 
//执行任务并获取Future对象 
Future f1 = pool.submit(c1); 
Future f2 = pool.submit(c2); 
//从Future对象上获取任务的返回值，并输出到控制台 
System.out.println(">>>"+f1.get().toString()); 
System.out.println(">>>"+f2.get().toString()); 
//关闭线程池 
pool.shutdown(); 
} 
} 

class MyCallable implements Callable{ 
private String oid; 

MyCallable(String oid) { 
this.oid = oid; 
} 

@Override 
public Object call() throws Exception { 
return oid+"任务返回的内容"; 
} 
}