使用2个不同的类别打印偶数和奇数

Question

这是我在求职面试中提出的一个问题:

你有两个不同的类(实现Runnable)说EvenThread和OddThread.顾名思义,EvenThread只打印偶数,奇数线程只打印奇数,考虑范围为0-100.

class EvenThread implements Runnable {

    @Override
    public void run() {
        for (int i = 0; i <= 10; i += 2) {
            System.out.println(i);
        }
    }
}

class OddThread implements Runnable {

    @Override
    public void run() {
        for (int i = 1; i < 10; i += 2) {
            System.out.println(i);
        }
    }
}

public class EvenOdd {

    public static void main(String args[]) {
        Thread tEven = new Thread(new EvenThread());
        Thread tOdd = new Thread(new OddThread());

        tEven.start();
        tOdd.start();
    }
}

现在我们需要以这样的方式强制执行机制:数字按顺序打印(即0,1,2,3,4 ......等等).

我在Stack Overflow中看到了很多类似的问题,但它们只有一个类来打印数字,并且在其中调用了2个同步方法.

任何专家都可以建议吗？

Answer 1

这是一个带有低级等待/通知机制的丑陋示例：

public class Main {
    static boolean turn = false; // false is even, true is odd

    public static void main(String[] args) {
        Object o = new Object();
        Thread tEven = new Thread(new EvenThread(o));
        Thread tOdd = new Thread(new OddThread(o));

        tEven.start();
        tOdd.start();
    }

    // TODO some inheritance with [Even/Odd]Thread

    static class EvenThread implements Runnable {
        Object o;

        EvenThread(Object o) {
            this.o = o;
        }

        @Override
        public void run() {
            for (int i = 0; i <= 10; i += 2) {
                synchronized (o) {
                    try {
                        while (turn) {
                            o.wait();
                        }
                    }
                    catch (InterruptedException ie) {
                        ie.printStackTrace();
                    }
                    finally {
                        System.out.println(i);
                        turn = !turn;
                        o.notifyAll();
                    }
                }
            }
        }
    }

    static class OddThread implements Runnable {
        Object o;

        OddThread(Object o) {
            this.o = o;
        }

        @Override
        public void run() {
            for (int i = 1; i < 10; i += 2) {
                synchronized (o) {
                    try {
                        while (!turn) {
                            o.wait();
                        }
                    }
                    catch (InterruptedException ie) {
                        ie.printStackTrace();
                    }
                    finally {
                        System.out.println(i);
                        turn = !turn;
                        o.notifyAll();
                    }
                }
            }
        }
    }
}

输出

0
1
2
3
4
5
6
7
8
9
10