Java多线程-2-常用的实现多线程的两种方式

Thread和Runnable

1、简介

Runnable是一个接口，该接口中只包含了一个run()方法。它的定义为：

public interface Runnable
{
    public abstract void run()
}

Runnable的作用为实现多线程。我们可以定义一个类A，实现Runnable接口；然后通过new Thread(new A())方式新建线程

Thread是一个类，它背身就实现了Runnable接口。它的声明为：

public class Thread implements Runnable{}

Thread类的作用，也是实现多线程

2、Thread和Runnable的异同点

相同点：都是“多线程”的实现方式

不同点：(1)、Thread是类，而Runnable是接口；Thread本身是实现了Runnable接口的类。而一个类只能继承一个父类，却可以实现多个接口，因此Runnable具有更好的扩展性；(2)、Runnable还可以用于“资源共享”，即，多个线程都是基于某一个Runnable对象建立的，它们会共享Runnable对象上的资源。

3、Thread的多线程示例

class MyThread extends Thread
{
    private int ticket = 10;
    public void run()
    {
        for(int i = 0;i < 20;i++)
        {
            if(this.ticket > 0)
                System.out.println(this.getName()+" sells a ticket. Before this we have:"+this.ticket--);
        }
    }
}

public class problem1 
{    
    public static void main(String[] args)
    {
        MyThread t1 = new MyThread();
        MyThread t2 = new MyThread();
        MyThread t3 = new MyThread();
        t1.start();
        t2.start();
        t3.start();
    }
}

运行结果为：

Thread-1 sells a ticket. Before this we have:10
Thread-0 sells a ticket. Before this we have:10
Thread-0 sells a ticket. Before this we have:9
Thread-0 sells a ticket. Before this we have:8
Thread-0 sells a ticket. Before this we have:7
Thread-0 sells a ticket. Before this we have:6
Thread-0 sells a ticket. Before this we have:5
Thread-0 sells a ticket. Before this we have:4
Thread-0 sells a ticket. Before this we have:3
Thread-0 sells a ticket. Before this we have:2
Thread-2 sells a ticket. Before this we have:10
Thread-2 sells a ticket. Before this we have:9
Thread-2 sells a ticket. Before this we have:8
Thread-2 sells a ticket. Before this we have:7
Thread-2 sells a ticket. Before this we have:6
Thread-2 sells a ticket. Before this we have:5
Thread-2 sells a ticket. Before this we have:4
Thread-2 sells a ticket. Before this we have:3
Thread-2 sells a ticket. Before this we have:2
Thread-2 sells a ticket. Before this we have:1
Thread-0 sells a ticket. Before this we have:1
Thread-1 sells a ticket. Before this we have:9
Thread-1 sells a ticket. Before this we have:8
Thread-1 sells a ticket. Before this we have:7
Thread-1 sells a ticket. Before this we have:6
Thread-1 sells a ticket. Before this we have:5
Thread-1 sells a ticket. Before this we have:4
Thread-1 sells a ticket. Before this we have:3
Thread-1 sells a ticket. Before this we have:2
Thread-1 sells a ticket. Before this we have:1

结果说明：

(1)、MyThread类继承于Thread类，它是自定义的线程。每个MyThread会卖出10张票

(2)、主线程main创建并启动了3个MyThread子线程。每个子线程都各自卖出了10张票

4、Runnable的多线程示例

class MyThread implements Runnable
{
    private int ticket = 10;
    public void run()
    {
        for(int i = 0;i < 20;i++)
        {
            if(this.ticket > 0)
                System.out.println(Thread.currentThread().getName() + " sells a ticket. Before this we have:"+this.ticket--);
        }
    }
}

public class problem1 
{    
    public static void main(String[] args)
    {
        MyThread mt =  new MyThread();
        
        Thread t1 = new Thread(mt);
        Thread t2 = new Thread(mt);
        Thread t3 = new Thread(mt);
        
        t1.start();
        t2.start();
        t3.start();
    }
}

运行结果为：

Thread-0 sells a ticket. Before this we have:10
Thread-0 sells a ticket. Before this we have:7
Thread-2 sells a ticket. Before this we have:8
Thread-2 sells a ticket. Before this we have:5
Thread-1 sells a ticket. Before this we have:9
Thread-2 sells a ticket. Before this we have:4
Thread-0 sells a ticket. Before this we have:6
Thread-2 sells a ticket. Before this we have:2
Thread-1 sells a ticket. Before this we have:3
Thread-0 sells a ticket. Before this we have:1

结果说明：

(1)、和上面的MyThread类继承于Thread类不同，这里的MyThread实现了Runnable接口

(2)、主线程main创建并启动了三个子线程，而且这三个子线程都是基于"mt"这个Runnable对象创建的。运行结果是这三个子线程一共卖出了10张票，这说明它们是共享资源的