1116. Print Zero Even Odd

class ZeroEvenOdd {
    private int n;
    private final Object lock;
    private boolean shouldPrintZero;
    private boolean shouldPrintOdd;

    public ZeroEvenOdd(int n) {
        this.n = n;
        this.lock = new Object();
        this.shouldPrintZero = true;
        this.shouldPrintOdd = true;
    }

    // order: zero, odd, zero, even

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            synchronized (lock) {
                while (!shouldPrintZero) {
                    lock.wait();
                }

                printNumber.accept(0);

                shouldPrintZero = false;
                lock.notifyAll();
            }
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for (int i = 2; i <= n; i += 2) {
            synchronized (lock) {
                while (shouldPrintZero || shouldPrintOdd) {
                    lock.wait();
                }

                printNumber.accept(i);

                shouldPrintZero = true;
                shouldPrintOdd = true;
                lock.notifyAll();
            }
        }
    }

    public synchronized void odd(IntConsumer printNumber) throws InterruptedException {
        for (int i = 1; i <= n; i += 2) {
            synchronized (lock) {
                while (shouldPrintZero || !shouldPrintOdd) {
                    lock.wait();
                }

                printNumber.accept(i);

                shouldPrintZero = true;
                shouldPrintOdd = false;
                lock.notifyAll();
            }
        }
    }

}

注意该题在调用时三个线程只会调用一次，所以需要在方法内部进行 for 循环处理。

References

1116. Print Zero Even Odd