class MyThread extends Thread {
    private int ticket = 5;
    private String name;
    public MyThread(String name) {
        this.name = name;
    }
    public void run() {
/*        for(int i = 0;i < 10; i++)
            System.out.println(name + "运行， i = " + i);   */

        for(int i = 0;i<10;i++){
            if(ticket > 0)
                System.out.println(name + "卖票:ticket = " + ticket--);
        }  
    }
}

public class ThreadDemo01 {
    public static void main (String args[]) {
        MyThread mt1 = new MyThread("线程A");
        MyThread mt2 = new MyThread("线程B");
        MyThread mt3 = new MyThread("线程C");
        mt1.start();
        mt2.start();
        mt3.start();
    }
}

运行结果：
线程A卖票:ticket = 5
线程A卖票:ticket = 4
线程A卖票:ticket = 3
线程A卖票:ticket = 2
线程A卖票:ticket = 1
线程B卖票:ticket = 5
线程B卖票:ticket = 4
线程B卖票:ticket = 3
线程B卖票:ticket = 2
线程B卖票:ticket = 1
线程C卖票:ticket = 5
线程C卖票:ticket = 4
线程C卖票:ticket = 3
线程C卖票:ticket = 2
线程C卖票:ticket = 1

为什么3个线程不是交错运行的

循环次数太少，当线程A运行完了，线程B还没有启动，因此3个线程不是交错运行。
如果将ticket 改为 5000; 循环次数改为6000，3个线程是交错运行的