通过实现Runnable接口来实现多线程

在jdk中有一个Thread(Runnable target)构造方法。Runnable接口只有一个run方法。

当使用Thread(Runnable target)方法创建线程对象时，需为该方法传递一个Runnable接口的类对象。这样创建的线程将调用那个实现了Runnable接口的类对象中的run方法作为其运行代码，而不再调用Thread类中的run方法。

public class ThreadDemo3 {

    public static void main(String[] args) {

        TestThread3 tt = new TestThread3();
        Thread t = new Thread(tt);
        t.start();
        while(true){
            System.out.println("main thread is runing...");
            try {
                Thread.currentThread().sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class TestThread3 implements Runnable{

    @Override
    public void run() {
        while(true){
            System.out.println(Thread.currentThread().getName() + " is runing***");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

}

测试运行结果：
main thread is runing...
main thread is runing...
Thread-0 is runing***
main thread is runing...
Thread-0 is runing***
main thread is runing...
Thread-0 is runing***
main thread is runing...
Thread-0 is runing***
main thread is runing...
Thread-0 is runing***
main thread is runing...
Thread-0 is runing***
Thread-0 is runing***

实现runnable接口相对于继承Thread类来说，有如下好处：
适合多个相同程序代码的线程去处理同一资源的情况。
可以避免由于java的单继承带来的局限。
代码能被多个线程共享，代码与数据是独立的。

事实上，几乎所有的多线程应用都可通过实现Runnable接口来实现。