一道线程面试题

2个线程交替打印1-100内的数，线程A打印偶数，线程B打印奇数

打印结果如下：

A: 0
B: 1
A: 2
B: 3
A: 4
B: 5
......

实现代码

public class printNum{

    public static void main(String[] args) {
        ThreadPrintNum threadPrintNum = new ThreadPrintNum();
        new Thread(() -> {
            for (int i = 0; i <= 100; i += 2) {
                threadPrintNum.printEven(i);
            }
        },"A").start();
        new Thread(() -> {
            for (int i = 1; i < 100; i += 2) {
                threadPrintNum.printOdd(i);
            }
        },"B").start();
    }
}

class ThreadPrintNum {
    private int num = 1;

    private ReentrantLock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();

    /**
     * 打印偶数
     * @param i
     */
    public void printEven(int i){
        lock.lock();
        try {
            if(num != 1){
                condition1.await();
            }
            System.out.println(Thread.currentThread().getName() + ": " + i);
            num = 2;
            condition2.signal();
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    /**
     * 打印奇数
     * @param i
     */
    public void printOdd(int i){
        lock.lock();
        try {
            if (num != 2){
                condition2.await();
            }
            System.out.println(Thread.currentThread().getName() + ": " + i);
            num = 1;
            condition1.signal();
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}