Random rand = new Random(0);
    int keyBits = 32;
    int hashBits = function.bits();
    for (int i = 0; i < keyBits; i++) {
      int[] same = new int[hashBits];
      int[] diff = new int[hashBits];
      // go through trials to compute probability
      for (int j = 0; j < trials; j++) {
        int key1 = rand.nextInt();
        // flip input bit for key2