LeetCode 1116. Print Zero Even Odd

Description:
Suppose you are given the following code:

class ZeroEvenOdd {
public ZeroEvenOdd(int n) { … } // constructor
public void zero(printNumber) { … } // only output 0’s
public void even(printNumber) { … } // only output even numbers
public void odd(printNumber) { … } // only output odd numbers
}
The same instance of ZeroEvenOdd will be passed to three different threads:

Thread A will call zero() which should only output 0’s.
Thread B will call even() which should only ouput even numbers.
Thread C will call odd() which should only output odd numbers.
Each of the threads is given a printNumber method to output an integer. Modify the given program to output the series 010203040506… where the length of the series must be 2n.

Example 1:

Input: n = 2
Output: “0102”
Explanation: There are three threads being fired asynchronously. One of them calls zero(), the other calls even(), and the last one calls odd(). “0102” is the correct output.

Solution:

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class ZeroEvenOdd {
    private int n;
    
    private volatile boolean iszero = true;
    private volatile boolean isodd = true;
    private volatile boolean iseven = false;
    
    private Object lock = new Object();
    
    public ZeroEvenOdd(int n) {
        this.n = n;
    }
    
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for(int i = 0; i < n; i++) {
            synchronized (lock) {
                while(!iszero)
                    lock.wait();
                printNumber.accept(0);
                iszero = false;
                lock.notifyAll();
            }
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for(int i = 2; i <= n; i += 2){
            synchronized(lock){
                while(iszero || !iseven)
                    lock.wait();
                printNumber.accept(i);
                iseven = false;
                iszero = true;
                isodd = true;
                lock.notifyAll();
            }
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for(int i = 1; i <= n; i += 2) {
            synchronized(lock) {
                while(iszero || !isodd) 
                    lock.wait();
                printNumber.accept(i);
                iseven = true;
                isodd = false;
                iszero = true;
                lock.notifyAll();
            }
        }
    }
}