老生常谈java中的Future模式

ExecutorService executor = Executors.newSingleThreadExecutor();Future<String> future = executor.submit(callable); //主线程需要callable线程的结果，先拿到一个未来的FutureSystem.out.println(future.get()); //有了结果后再根据get方法取真实的结果,当然如果此时callable线程如果没有执行完get方法会阻塞执行完，如果执行完则直接返回结果或抛出异常

package com.future;/** * 数据结果 * Created by yulinfeng on 6/18/17. */public interface Data { String getResult() throws InterruptedException;}

package com.future;/** * 结果的真实计算过程 * Created by yulinfeng on 6/18/17. */public class RealData implements Data { protected String data; public RealData(String data) {  try {   System.out.println("正在计算结果");   Thread.sleep(3000);  //模拟计算  } catch (InterruptedException e) {   e.printStackTrace();  }  this.data = data + “ world”; } public String getResult() throws InterruptedException {  return data; }}

package com.future;/** * 真实结果RealData的代理 * Created by yulinfeng on 6/18/17. */public class FutureData implements Data { RealData realData = null; //对RealData的封装，代理了RealData boolean isReady = false; //真实结果是否已经准备好 public synchronized void setResultData(RealData realData) {  if (isReady) {   return;  }  this.realData = realData;  isReady = true;  notifyAll(); //realData已经被注入到了futureData中，通知getResult方法 } public synchronized String getResult() throws InterruptedException {  if (!isReady) {   wait();  //数据还未计算好，阻塞等待  }  return realData.getResult(); }}

package com.future;/** * Client主要完成的功能包括：1. 返回一个FutureData；2.开启一个线程用于构造RealData * Created by yulinfeng on 6/18/17. */public class Client { public Data request(final String string) {  final FutureData futureData = new FutureData();  /*计算过程比较慢，单独放到一个线程中去*/  new Thread(new Runnable() {   public void run() {    RealData realData = new RealData(string);    futureData.setResultData(realData);   }  }).start();  return futureData; //先返回一个“假”的futureData }}

/** * 负责调用Client发起请求，并使用返回的数据。 * 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("准备计算结果");  Data data = client.request("hello"); //立即返回一个“假”的futureData，可以不用阻塞的等待数据返回，转而执行其它任务  System.out.println("执行其它任务");  Thread.sleep(3000);  //模拟执行其它任务  System.out.println("数据的计算结果为：" + data.getResult()); }}

package com.future;import java.util.concurrent.Callable;/** * 结果的真实计算过程 * 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("正在计算结果");   Thread.sleep(2000);  //模拟计算结果  } 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;/** * 负责调用Executor的submit，并使用返回的数据。 * Created by yulinfeng on 6/18/17. */public class Main2 { public static void main(String[] args) throws InterruptedException, ExecutionException {  ExecutorService client = Executors.newSingleThreadExecutor(); //类似Client  System.out.println("准备计算结果");  Future<String> data = client.submit(new RealData2("hello")); //类似Client.request  System.out.println("执行其它任务");  Thread.sleep(3000);  System.out.println("数据的计算结果为：" + data.get()); }}

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