多线程系列02-实现多线程的方式

常见的实现多线程的方式：Thread和Runnable
其他方式：实现Callable接口通过Future/FutureTask包装器来创建Thread线程，通过线程池实现有返回结果的线程

1. Runnable，Runnable是一个接口，仅包含了一个run()方法。

@FunctionalInterface
public interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

Runnable实例

public class MyThread2 implements Runnable {

    private int ticket = 20;
    @Override
    public void run() {
        for(int i=0;i<30;i++){
            if(this.ticket>0){
                System.out.println(Thread.currentThread().getName()+" 卖票：ticket"+this.ticket--);
            }
        }
    }

    public static void main(String[] args) {

        MyThread2 myThread2 = new MyThread2();

        //主线程main创建并启动3个子线程，而且这3个子线程都是基于“myThread2这个Runnable对象”而创建的。这3个子线程一共卖出了20张票。
        //这3个子线程可能会由于并发问题，导致卖出多余20张票
        Thread t1 = new Thread(myThread2);
        Thread t2 = new Thread(myThread2);
        Thread t3 = new Thread(myThread2);

        t1.start();
        t2.start();
        t3.start();
    }
}

运行结果

Thread-0 卖票：ticket20 ——并发
Thread-1 卖票：ticket20 
Thread-2 卖票：ticket19
Thread-1 卖票：ticket17
Thread-0 卖票：ticket18
Thread-1 卖票：ticket15
Thread-2 卖票：ticket16
Thread-1 卖票：ticket13
Thread-1 卖票：ticket11
Thread-1 卖票：ticket10
Thread-1 卖票：ticket9
Thread-0 卖票：ticket14
Thread-1 卖票：ticket8
Thread-2 卖票：ticket12
Thread-1 卖票：ticket6
Thread-0 卖票：ticket7
Thread-1 卖票：ticket4
Thread-0 卖票：ticket3
Thread-0 卖票：ticket2
Thread-2 卖票：ticket5
Thread-1 卖票：ticket1

结果说明：
(01) 和下面“MyThread继承于Thread”不同；这里的MyThread实现了Runnable接口。
(02) 主线程main创建并启动3个子线程，而且这3个子线程都是基于“myThread2这个Runnable对象”而创建的。运行结果是这3个子线程一共卖出了20张票。这说明它们是共享了MyThread接口的。
(03) 因为并发的原因导致可能多余20张票。
Runnable实现了资源的共享。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。
通常，建议通过“Runnable”实现多线程！

2. Thread，Thread本身是实现了Runnable接口的类。

public class MyThread1 extends Thread{

    private int ticket = 10;
    public void run(){
        for(int i=0; i<5; i++){
            if(this.ticket > 0){
                System.out.println(this.getName()+" 卖票：ticket"+this.ticket--);
            }
        }
    }

    public static void main(String[] args) {

        //主线程main()创建了3个MyThread子线程，每个子线程都各自卖出5张票
        MyThread1 t1 = new MyThread1();
        MyThread1 t2 = new MyThread1();
        MyThread1 t3 = new MyThread1();

        t1.start();
        t2.start();
        t3.start();
    }
}

运行结果

Thread-0 卖票：ticket10
Thread-1 卖票：ticket10
Thread-0 卖票：ticket9
Thread-1 卖票：ticket9
Thread-1 卖票：ticket8
Thread-1 卖票：ticket7
Thread-1 卖票：ticket6
Thread-0 卖票：ticket8
Thread-0 卖票：ticket7
Thread-0 卖票：ticket6
Thread-2 卖票：ticket10
Thread-2 卖票：ticket9
Thread-2 卖票：ticket8
Thread-2 卖票：ticket7
Thread-2 卖票：ticket6

结果说明：
(01) MyThread继承于Thread，它是自定义的线程。
(02) 主线程main创建并启动3个MyThread子线程。每个子线程都各自卖出了10张票。