多线程的创建方式之实现Callable接口

与实现Runable接口相比，Callable功能更强大

1.与run()方法相比，call()方法可以有返回值

2.call()方法可以抛出异常

3.call()方法支持泛型的返回值

4.call()方法的返回值以及线程的调用需要借助于FutureTask类来实现

5.FutureTask的run方法是线程安全的，使用的是CAS机制

示例代码：

package com.debuggg.exer;

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

class NumThread implements Callable {

    @Override
    public Object call() throws Exception {
        int sum = 0;
        for (int i = 0; i < 100; i++) {
            if(i % 2 == 0){
                sum += i;
                System.out.println(i);
            }
        }
        return sum;
    }
}

public class CallableTest {
    public static void main(String[] args) {
        NumThread numThread = new NumThread();

        FutureTask futureTask = new FutureTask(numThread);

        Thread thread = new Thread(futureTask);
        thread.start();

        try {
            int num = (int)futureTask.get();
            System.out.println(num);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

    }
}