Java线程之Callable接口实现线程

Callable接口实现线程

Callable接口性质概述

Callable接口是一种具有类型参数的泛型，它的类型参数是从call()方法中返回的值，而且必须使用ExecutorService.submit()方法调用它。下面是该接口的源码

public interface Callable<V> {       /**         * Computes a result, or throws an exception if unable to do so.         *          * @return computed result         * @throws Exception if unable to compute a result         */        V call() throws Exception;}

从注释中我们可以看到，call()方法不仅可以返回值，而且还能抛出异常。

Callable接口的简单用法实例

下面是我根据Callable接口的性质，写的简单地应用实例。

首先，定义一个类它实现了Callable接口，

public class CallableTest implements Callable<String>{private String name;public CallableTest(String name){this.name = name;}@Overridepublic String call() throws Exception {return name;}}

注意，Callable中泛型的类型要与call()方法返回的类型一致。然后，我们再定义一个类测试结果

public class CallableMain {public static void main(String[] args){ExecutorService exec = Executors.newCachedThreadPool();Future<String> fu = exec.submit(new CallableTest("test"));try {System.out.println("Callable return is " + fu.get());} catch (InterruptedException | ExecutionException e) {e.printStackTrace();}}}

Callable接口的返回的是Future接口的实例化的类，所以需要这个接口来接收。调用Future接口中的get()方法来去的返回值。

基于Callable接口实现查找一组序列中最大值的程序

public class FindMax implements Callable<Integer>{private int[] array;private int start;private int end;public FindMax(int[] A,int start,int end){this.array = A;this.start = start;this.end = end;}@Overridepublic Integer call() throws Exception {int max = Integer.MIN_VALUE;for(int i = start; i < end; i++){if(max < array[i]){max = array[i];}}return max;}}

public class Main {public static void main(String[] args){int[] array = {8,7,2,3,4,5,1,5,3,9,0,1,8};int length = array.length;ExecutorService exec = Executors.newCachedThreadPool();Future<Integer> fu1 = exec.submit(new FindMax(array,0,length/2));Future<Integer> fu2 = exec.submit(new FindMax(array,length/2+1,length));try {if(fu1.get() > fu2.get()){System.out.println("The max is " + fu1.get());}else{System.out.println("The max is " + fu2.get());}} catch (InterruptedException | ExecutionException e) {e.printStackTrace();}exec.shutdown();}}

这里主要是根据数组的下标划分两个子数组。