ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(callable); //主線程需要callable線程的結(jié)果，先拿到一個未來的Future
System.out.println(future.get()); //有了結(jié)果后再根據(jù)get方法取真實的結(jié)果,當然如果此時callable線程如果沒有執(zhí)行完get方法會阻塞執(zhí)行完，如果執(zhí)行完則直接返回結(jié)果或拋出異常

package com.future;

/**
 * 數(shù)據(jù)結(jié)果
 * Created by yulinfeng on 6/18/17.
 */
public interface Data {
 String getResult() throws InterruptedException;
}

package com.future;

/**
 * 結(jié)果的真實計算過程
 * Created by yulinfeng on 6/18/17.
 */
public class RealData implements Data {
 protected String data;

 public RealData(String data) {
  try {
   System.out.println("正在計算結(jié)果");
   Thread.sleep(3000);  //模擬計算
  } catch (InterruptedException e) {
   e.printStackTrace();
  }
  this.data = data + “ world”;
 }

 public String getResult() throws InterruptedException {
  return data;
 }
}

package com.future;

/**
 * 真實結(jié)果RealData的代理
 * Created by yulinfeng on 6/18/17.
 */
public class FutureData implements Data {
 RealData realData = null; //對RealData的封裝，代理了RealData
 boolean isReady = false; //真實結(jié)果是否已經(jīng)準備好

 public synchronized void setResultData(RealData realData) {
  if (isReady) {
   return;
  }
  this.realData = realData;
  isReady = true;
  notifyAll(); //realData已經(jīng)被注入到了futureData中，通知getResult方法
 }

 public synchronized String getResult() throws InterruptedException {
  if (!isReady) {
   wait();  //數(shù)據(jù)還未計算好，阻塞等待
  }
  return realData.getResult();
 }
}

package com.future;

/**
 * Client主要完成的功能包括：1. 返回一個FutureData；2.開啟一個線程用于構(gòu)造RealData
 * Created by yulinfeng on 6/18/17.
 */
public class Client {

 public Data request(final String string) {
  final FutureData futureData = new FutureData();

  /*計算過程比較慢，單獨放到一個線程中去*/
  new Thread(new Runnable() {

   public void run() {
    RealData realData = new RealData(string);
    futureData.setResultData(realData);
   }
  }).start();

  return futureData; //先返回一個“假”的futureData
 }
}

/**
 * 負責調(diào)用Client發(fā)起請求，并使用返回的數(shù)據(jù)。
 * Created by yulinfeng on 6/18/17.
 */
public class Main {
 public static void main(String[] args) throws InterruptedException {
  Client client = new Client();
  System.out.println("準備計算結(jié)果");
  Data data = client.request("hello"); //立即返回一個“假”的futureData，可以不用阻塞的等待數(shù)據(jù)返回，轉(zhuǎn)而執(zhí)行其它任務(wù)
  System.out.println("執(zhí)行其它任務(wù)");
  Thread.sleep(3000);  //模擬執(zhí)行其它任務(wù)
  System.out.println("數(shù)據(jù)的計算結(jié)果為：" + data.getResult());
 }
}

package com.future;

import java.util.concurrent.Callable;

/**
 * 結(jié)果的真實計算過程
 * Created by yulinfeng on 6/18/17.
 */
public class RealData2 implements Callable<String> {
 protected String data;

 public RealData2(String data) {
  this.data = data;
 }
 public String call() throws Exception {
  try {
   System.out.println("正在計算結(jié)果");
   Thread.sleep(2000);  //模擬計算結(jié)果
  } catch (InterruptedException e) {
   e.printStackTrace();
  }
  this.data = data + " world";
  return data;
 }
}

package com.future;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
 * 負責調(diào)用Executor的submit，并使用返回的數(shù)據(jù)。
 * Created by yulinfeng on 6/18/17.
 */
public class Main2 {

 public static void main(String[] args) throws InterruptedException, ExecutionException {
  ExecutorService client = Executors.newSingleThreadExecutor(); //類似Client
  System.out.println("準備計算結(jié)果");
  Future<String> data = client.submit(new RealData2("hello")); //類似Client.request
  System.out.println("執(zhí)行其它任務(wù)");
  Thread.sleep(3000);
  System.out.println("數(shù)據(jù)的計算結(jié)果為：" + data.get());
 }
}

//ThreadPoolExecutor$Worker#runWorker
task.run();