遇到一個面試題需要3個執行緒順序執行，並迴圈10次，程式碼如下：

public class MyThread extends Thread {

    private Object lock;
    private String showChar;
    private int showNumPosition;

    private int printCount = 0;

    volatile private static int addNumber = 1;

    public MyThread(Object lock, String showChar, int showNumPosition) {
        super
 
();
        this.lock = lock;
        this.showChar = showChar;
        this.showNumPosition = showNumPosition;
    }

    @Override
    public void run() {
        try {
            synchronized (lock) {
                while (true) {
                    if (addNumber % 3 == showNumPosition) {
                        System.out.println("ThreadName="
 

                                + Thread.currentThread().getName()
                                + " runCount=" + addNumber + " " + showChar);
                        lock.notifyAll();
                        addNumber++;
                        printCount++;
                        if (printCount == 10
 
) {
                            break;
                        }
                    } else {
                        lock.wait();
                    }
                }
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}

public class Run {

    public static void main(String[] args) {

        Object lock = new Object();

        MyThread a = new MyThread(lock, "A", 1);
        MyThread b = new MyThread(lock, "B", 2);
        MyThread c = new MyThread(lock, "C", 0);

        a.start();
        b.start();
        c.start();

    }

}

執行結果如下

ThreadName=Thread-0 runCount=1 A
ThreadName=Thread-1 runCount=2 B
ThreadName=Thread-2 runCount=3 C
ThreadName=Thread-0 runCount=4 A
ThreadName=Thread-1 runCount=5 B
ThreadName=Thread-2 runCount=6 C
ThreadName=Thread-0 runCount=7 A
ThreadName=Thread-1 runCount=8 B
ThreadName=Thread-2 runCount=9 C
ThreadName=Thread-0 runCount=10 A
ThreadName=Thread-1 runCount=11 B
ThreadName=Thread-2 runCount=12 C
ThreadName=Thread-0 runCount=13 A
ThreadName=Thread-1 runCount=14 B
ThreadName=Thread-2 runCount=15 C
ThreadName=Thread-0 runCount=16 A
ThreadName=Thread-1 runCount=17 B
ThreadName=Thread-2 runCount=18 C
ThreadName=Thread-0 runCount=19 A
ThreadName=Thread-1 runCount=20 B
ThreadName=Thread-2 runCount=21 C
ThreadName=Thread-0 runCount=22 A
ThreadName=Thread-1 runCount=23 B
ThreadName=Thread-2 runCount=24 C
ThreadName=Thread-0 runCount=25 A
ThreadName=Thread-1 runCount=26 B
ThreadName=Thread-2 runCount=27 C
ThreadName=Thread-0 runCount=28 A
ThreadName=Thread-1 runCount=29 B
ThreadName=Thread-2 runCount=30 C