Callable与Future应用

应用于异步的任务执行,类似JS的回调方法.

Future取得的结果类型与Callable返回的结果类型必须一致.

如异步执行方式:

public class FutureTaskDemo {public static void main(String[] args) {// 初始化一个Callable对象和FutureTask对象Callable<Object> pAccount = new PrivateAccount();FutureTask<Object> futureTask = new FutureTask<Object>(pAccount);// 使用FutureTask创建一个线程Thread pAccountThread = new Thread(futureTask);System.out.println("future task starts at " + System.nanoTime());pAccountThread.start();// 主线程执行自己的任务System.out.println("main thread doing something else here.");// 从其他帐户获取总金额int totalMoney = new Random().nextInt(100000);System.out.println(" You have " + totalMoney + " in your other Accounts. ");System.out.println(" Waiting for data from Private Account");// 测试后台的就计算线程是否完成，如果未完成，等待while(!futureTask.isDone()){try {Thread.sleep(5);} catch (InterruptedException e) {e.printStackTrace();}}System.out.println("future task ends at " + System.nanoTime());Integer privataAccountMoney = null;// 如果后台的FutureTask计算完成，则返回计算结果try {privataAccountMoney = (Integer) futureTask.get();} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}System.out.println(" The total money you have is " + (totalMoney + privataAccountMoney.intValue()));}}// 创建一个Callable类，模拟计算一个私有帐户中的金额class PrivateAccount implements Callable<Object> {Integer totalMoney;@Overridepublic Integer call() throws Exception{Thread.sleep(5000);totalMoney = new Integer(new Random().nextInt(10000));System.out.println(" You have " + totalMoney + " in your private Account. ");return totalMoney;}}

?采用ExecutorSevice的submit方法提交:

public class CallableAndFuture {public static void main(String[] args) {// Future(将来)取得的结果类型和Callable返回的结果类型必须一致.// Callable要采用ExecutorSevice的submit方法提交，返回的future对象可以取消任务.ExecutorService threadPool =  Executors.newSingleThreadExecutor();Future<String> future =threadPool.submit(new Callable<String>() {public String call() throws Exception {Thread.sleep(2000);return "hello";};});System.out.println("等待结果");try {// 一直等待结果System.out.println("拿到结果：" + future.get());} catch (InterruptedException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}threadPool.shutdown();// CompletionService用于提交一组Callable任务，其take方法返回已完成的一个Callable任务// 对应的Future对象,好比N块麦子，谁先成熟先收。ExecutorService threadPool2 =  Executors.newFixedThreadPool(10);CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);for(int i=1;i<=10;i++){final int seq = i;completionService.submit(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {Thread.sleep(new Random().nextInt(5000));return seq;}});}for(int i=0;i<10;i++){try {// 先完成的先得到System.out.println(completionService.take().get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}}threadPool2.shutdown();}}