8.1-多线程创建方法

一、继承Thread类

Thread是一个实现了Runnable 接口的实例。

public class ThreadDemo extends Thread {
    public void run(){
        System.out.println(" MyThread.run()");
    }
    public static void main(String args[]){
        ThreadDemo demo1 = new ThreadDemo();
        ThreadDemo demo2 = new ThreadDemo();
        Thread demo3 = new Thread(new RunnableDemo());
        demo1.start();
        demo2.start();
        demo3.start();
    }
}

二、实现Runnable接口

实现接口后，需要重写Run方法。通过 new Thread(xxx) 方法获得实例化的 线程对象。

public class RunnableDemo implements Runnable{
    public void run(){
        System.out.println(" Runnabl3 Demo");
    }
}

三、Executor框架

ExectutorService、Callable、Future 类配合使用，可以创建有返回结果的多线程。

主类，构建线程池。

import java.util.ArrayList;
import java.util.concurrent.*;
import java.util.List;
public class FutureDemo {
    public static void main(String args[]) throws ExecutionException, InterruptedException {
        int taskSize = 5;
        ExecutorService pool = Executors.newFixedThreadPool(5);
        List<Future> futureList = new ArrayList();
        for(int i=0; i<taskSize; i++){
            Callable c = new RuntimeCallable(i);
            Future f = pool.submit(c);
            futureList.add(f);
        }
        pool.shutdown();
        for(Future f : futureList){
            System.out.println(f.get());
        }
    }
}

继承Callable接口，得到线程执行类。 call方法是具体的执行逻辑。

import java.util.concurrent.*;
import java.util.Date;
import java.util.Random;
public class RuntimeCallable implements  Callable<Object>{
    public String name;
    public RuntimeCallable(int i){
        this.name = "thread-"+i;
    }
    public Object call() throws Exception {
        Date start = new Date();
        Random random = new Random();
        Thread.sleep(random.nextInt(1000));
        Date end = new Date();
        return end.getTime() - start.getTime();
    }
}