Find duplicates in Array in O(N) time

class Leet442 {
  
    public static void main(String args[])
    {
        int numRay[] = { 0, 4, 3, 2, 7, 8, 2, 3, 1 };
  
        for (int i = 0; i < numRay.length; i++) {
            numRay[numRay[i] % numRay.length]
                = numRay[numRay[i] % numRay.length]
                  + numRay.length;
        }
        System.out.println("The repeating elements are : ");
        for (int i = 0; i < numRay.length; i++) {
            if (numRay[i] >= numRay.length * 2) {
                System.out.println(i + " ");
            }
        }
    }
}