1195. Fizz Buzz Multithreaded 

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class FizzBuzz {

    private enum State {
        FIZZ, BUZZ, FIZZBUZZ, NUM
    }

    private final Object lock = new Object();
    private final int n;
    private State state;

    public FizzBuzz(int n) {
        this.n = n;
        this.state = State.NUM;
    }

    // printFizz.run() outputs "fizz".
    public void fizz(Runnable printFizz) throws InterruptedException {
        for (int i = 3; i <= n; i += 3) {
            if (i % 5 == 0) {
                continue;
            }

            synchronized (lock) {
                while (state != State.FIZZ) {
                    lock.wait();
                }

                printFizz.run();
                switchState(i);
                lock.notifyAll();
            }
        }
    }

    private void switchState(int i) {
        int nextNum = i + 1;
        if (nextNum % 3 == 0 && nextNum % 5 != 0) {
            state = State.FIZZ;
        } else if (nextNum % 5 == 0 && nextNum % 3 != 0) {
            state = State.BUZZ;
        } else if (nextNum % 3 == 0 && nextNum % 5 == 0) {
            state = State.FIZZBUZZ;
        } else {
            state = State.NUM;
        }
    }

    // printBuzz.run() outputs "buzz".
    public void buzz(Runnable printBuzz) throws InterruptedException {
        for (int i = 5; i <= n; i += 5) {
            if (i % 3 == 0) {
                continue;
            }

            synchronized (lock) {
                while (state != State.BUZZ) {
                    lock.wait();
                }

                printBuzz.run();
                switchState(i);
                lock.notifyAll();
            }
        }
    }

    // printFizzBuzz.run() outputs "fizzbuzz".
    public void fizzbuzz(Runnable printFizzBuzz) throws InterruptedException {
        for (int i = 15; i <= n; i += 15) {
            synchronized (lock) {
                while (state != State.FIZZBUZZ) {
                    lock.wait();
                }

                printFizzBuzz.run();
                switchState(i);
                lock.notifyAll();
            }
        }
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void number(IntConsumer printNumber) throws InterruptedException {
        for (int i = 1; i <= n; i++) {
            if (i % 3 == 0 || i % 5 == 0) {
                continue;
            }

            synchronized (lock) {
                while (state != State.NUM) {
                    lock.wait();
                }

                printNumber.accept(i);
                switchState(i);
                lock.notifyAll();
            }
        }
    }

}

References

1195. Fizz Buzz Multithreaded