13、Future Task

1、Future Task是什么

在Java中一般通过继承Thread类或者实现Runnable接口这两种方式来创建多线程，但是这两种方式都有个缺陷，就是不能在执行完成后获取执行的结果，因此Java 1.5之后提供了Callable和Future接口，通过它们就可以在任务执行完毕之后得到任务的执行结果

2、如何使用Future Task

package com.mmall.concurrency.example.aqs;

import lombok.extern.slf4j.Slf4j;

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

@Slf4j
public class FutureExample {

	static class MyCallable implements Callable<String> {

		@Override
		public String call() throws Exception {
			System.out.println("do something in callable");
			Thread.sleep(5000);
			return "Done";
		}
	}

	public static void main(String[] args) throws Exception {
		ExecutorService executorService = Executors.newCachedThreadPool();
		Future<String> future = executorService.submit(new MyCallable());
		System.out.println("do something in main");
		Thread.sleep(1000);
		String result = future.get();
		System.out.println("result：{}" + result);
	}
}

package com.mmall.concurrency.example.aqs;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

@Slf4j
public class FutureTaskExample {

	public static void main(String[] args) throws Exception {
		FutureTask<String> futureTask = new FutureTask<String>(new Callable<String>() {
			@Override
			public String call() throws Exception {
				System.out.println("do something in callable");
				Thread.sleep(5000);
				return "Done";
			}
		});

		new Thread(futureTask).start();
		System.out.println("do something in main");
		Thread.sleep(1000);
		String result = futureTask.get();
		System.out.println("result：{}" + result);
	}
}

3、为什么要使用Future Task

能获取到线程执行的结果