源码分析
这里只截取部分源码
Thread类
1 实现Runnable接口
public class Thread implements Runnable {}
2 有start()方法来启动线程
public synchronized void start() {
threadStatus != 0)
throw new IllegalThreadStateException();
3 有这样的构造方法:
public Thread(Runnable target) {
init(null, target, "Thread-" + nextThreadNum(), 0);
}
此方法可以接受Runnable的对象,换句话说就是Thread类可以启动Runnable实现的多线程.
Runnable接口
只有run方法,此方法不是线程的启动方法
public interface Runnable {
public abstract void run();
}
优缺点对比
实际开发中实现多线程肯定永远以实现Runnable接口为主
实现Runnable接口比继承Thread类有如下有点:
1 避免继承的局限,一个接口可以多实现
2 可以实现资源共享
实例
以卖票为例,总共10张票,3个窗口卖
public class MyThread extends Thread {
private int tickets = 10;
@Override
public void run() {
for (int i = 1; i <= 100; i++) {
if (tickets > 0) {
System.out.println(Thread.currentThread().getName() + "--卖出票: " + tickets--);
}
}
}
public static void main(String[] args) {
MyThread myThread1 = new MyThread();
MyThread myThread2 = new MyThread();
MyThread myThread3 = new MyThread();
myThread1.start();
myThread2.start();
myThread3.start();
}
}
运行结果如下:
Thread-1--卖出票: 1
Thread-0--卖出票: 1
Thread-2--卖出票: 1
Thread-0--卖出票: 2
Thread-0--卖出票: 3
Thread-0--卖出票: 4
Thread-0--卖出票: 5
Thread-0--卖出票: 6
Thread-0--卖出票: 7
Thread-0--卖出票: 8
Thread-0--卖出票: 9
Thread-0--卖出票: 10
Thread-1--卖出票: 2
Thread-1--卖出票: 3
Thread-1--卖出票: 4
Thread-1--卖出票: 5
Thread-1--卖出票: 6
Thread-1--卖出票: 7
Thread-1--卖出票: 8
Thread-1--卖出票: 9
Thread-1--卖出票: 10
Thread-2--卖出票: 2
Thread-2--卖出票: 3
Thread-2--卖出票: 4
Thread-2--卖出票: 5
Thread-2--卖出票: 6
Thread-2--卖出票: 7
Thread-2--卖出票: 8
Thread-2--卖出票: 9
Thread-2--卖出票: 10
每个线程都独立，不共享资源,如果真卖票就有问题了.
public class MyRunnable implements Runnable{
private int tickets = 10;
@Override
public void run() {
for (int i = 1; i <= 10; i++) {
if (tickets > 0) {
System.out.println(Thread.currentThread().getName() + "--卖出票: " + tickets--);
}
}
}
public static void main(String[] args) {
MyRunnable myRunnable = new MyRunnable();
Thread thread1 = new Thread(myRunnable, "窗口1");
Thread thread2 = new Thread(myRunnable, "窗口2");
Thread thread3 = new Thread(myRunnable, "窗口3");
thread1.start();
thread2.start();
thread3.start();
}
}
运行结果如下:
窗口1--卖出票: 10
窗口2--卖出票: 9
窗口2--卖出票: 8
窗口3--卖出票: 8
窗口1--卖出票: 7
窗口3--卖出票: 5
窗口2--卖出票: 6
窗口3--卖出票: 3
窗口3--卖出票: 1
窗口1--卖出票: 4
窗口2--卖出票: 2
可以看出每个线程共享了对象myRunnable的资源,卖出票的总数是对的.
