Suppose you are given the following code:

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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:

  1. Thread A will call zero() which should only output 0’s.
  2. Thread B will call even() which should only ouput even numbers.
  3. 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:

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Input: n = 5
Output: "0102030405"

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class ZeroEvenOdd {
    private int n;
    Semaphore zero = new Semaphore(1);
    Semaphore even = new Semaphore(0);
    Semaphore odd = new Semaphore(0);
    
    public ZeroEvenOdd(int n) {
        this.n = n;
    }

    // printNumber.accept(x) outputs "x", where x is an integer.
    public void zero(IntConsumer printNumber) throws InterruptedException {
        for (int i = 0; i < n; ++i) {
            zero.acquire();
            printNumber.accept(0);
            if (i % 2 == 0) odd.release();
            else even.release();
        }
    }

    public void even(IntConsumer printNumber) throws InterruptedException {
        for (int i = 2; i <= n; i += 2) {
            even.acquire();
            printNumber.accept(i);
            zero.release();
        }
    }

    public void odd(IntConsumer printNumber) throws InterruptedException {
        for (int i = 1; i <= n; i += 2) {
            odd.acquire();
            printNumber.accept(i);
            zero.release();
        }
    }
}