public class Main {  
  public static void main(String[] args) {  
    System.out.println("main BEGIN");  
    Host host = new Host();  
    Data data1 = host.request(10, 'A');  
    Data data2 = host.request(20, 'B');  
    Data data3 = host.request(30, 'C');  
    System.out.println("main otherJob BEGIN");  
    try {  
      Thread.sleep(200);  
    } catch (InterruptedException e) {  
    }  
    System.out.println("main otherJob END");  
    System.out.println("data1 = " + data1.getContent());  
    System.out.println("data2 = " + data2.getContent());  
    System.out.println("data3 = " + data3.getContent());  
    System.out.println("main END");  
  }  
} 

public class Host {  
  public Data request(final int count, final char c) {  
    System.out.println("request(" + count + ", " + c + ") BEGIN");  
    // (1) 建立FutureData的实体  
    final FutureData future = new FutureData();  
    // (2) 为了建立RealData的实体，启动新的线程  
    new Thread() {                     
      public void run() {  
       //在匿名内部类中使用count、future、c。            
        RealData realdata = new RealData(count, c);  
        future.setRealData(realdata);  
      }                         
    }.start();                       
    System.out.println("request(" + count + ", " + c + ") END");  
    // (3) 取回FutureData实体，作为传回值  
    return future;  
  }  
} 

public class RealData implements Data {  
  private final String content;  
  public RealData(int count, char c) {  
    System.out.println("making RealData(" + count + ", " + c + ") BEGIN");  
    char[] buffer = new char[count];  
    for (int i = 0; i < count; i++) {  
      buffer[i] = c;  
      try {  
        Thread.sleep(1000);  
      } catch (InterruptedException e) {  
      }  
    }  
    System.out.println("making RealData(" + count + ", " + c + ") END");  
    this.content = new String(buffer);  
  }  
  public String getContent() {  
    return content;  
  }  
}

public class FutureData implements Data {  
  private RealData realdata = null;  
  private boolean ready = false;  
  public synchronized void setRealData(RealData realdata) {  
    if (ready) {              
      return;   // 防止setRealData被调用两次以上。 
    }  
    this.realdata = realdata;  
    this.ready = true;  
    notifyAll();  
  }  
  public synchronized String getContent() {  
    while (!ready) {  
      try {  
        wait();  
      } catch (InterruptedException e) {  
      }  
    }  
    return realdata.getContent();  
  }  
}

System.out.println("data1 = " + data1.getContent()); 

while (!ready) {  
      try {  
        wait();  
      } catch (InterruptedException e) {  
      }  
//等做好后才能取到   
return realdata.getContent();