Java并发编程之Callable类和Future接口
2017-12-27 22:26
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1 Callable类和Future接口介绍
JDK5开始,Java创建多线程的方法新增了Callable接口,源码如下:public interface Callable<V> { V call() throws Exception; }相对使用Runnable接口或实现Thread类来创建多线程,其具2大优点:
1)Runnable接口或实现Thread类的run()方法不能声明异常抛出;而Callable接口的call()方法可以声明异常抛出;
2)Runnable接口或实现Thread类的run()方法是void类型,没有返回值;而Callable接口的call()方法可以有返回值,通过Future接口的get()方法可以获得Callable接口的返回值。
2 测试用例
2.1异常测试用例
public class MyCallable implements Callable<String> { private String name; public MyCallable(String name) { this.name = name; } @Override public String call() throws Exception{ //声明异常 Thread.sleep(5000); throw new InterruptedException(); //抛出异常 } } public class FutureApp1 { public static void main(String[] args) { ExecutorService executorService = Executors.newFixedThreadPool(1); MyCallable callable = new MyCallable("JayLai"); Future<String> future = executorService.submit(callable); try { //产生一个当前的毫秒,这个毫秒其实就是自1970年1月1日0时起的毫秒数 long time1 = System.currentTimeMillis(); System.out.println(future.get()); //get()方法是阻塞的 long time2 = System.currentTimeMillis(); System.out.println("阻塞时间为:" + (time2 - time1)+ "毫秒"); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } finally{ System.out.println("====end====="); } } }
测试结果:
2.2 返回值测试用例
public class MyCallable implements Callable<String> { private String name; public MyCallable(String name) { this.name = name; } @Override public String call() throws Exception{ //声明异常 Thread.sleep(5000); return name; } } public class FutureApp2{ public static void main(String[] args) { ExecutorService executorService = Executors.newFixedThreadPool(1); MyCallable callable = new MyCallable("JayLai"); Future<String> future = executorService.submit(callable); try { //产生一个当前的毫秒,这个毫秒其实就是自1970年1月1日0时起的毫秒数 long time1 = System.currentTimeMillis(); System.out.println("用户名: " + future.get()); //get()方法是阻塞的 long time2 = System.currentTimeMillis(); System.out.println("阻塞时间为:" + (time2 - time1)+ "毫秒"); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } finally{ System.out.println("====end====="); } } }
测试结果:
3 参考文献
[1] 高洪岩, Java多线程编程核心技术. 2015.[2] Goetz, B.等, Java 并发编程实战. 2012.
[3] https://docs.oracle.com/javase/8/docs/api/index.html
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