Algorithm Interview: Bit Convertision Between Two Integers

Interview Question:
Write a Java method that will return the number of bits that will need to be changed in order to convert an integer, X, into another integer, Y and vice versa. The method should accept two different integers as input.

Answer:
The key here is to use XOR operation z = x ^ y; to get the bit difference between them, then count the bit set in the result z.

public static int bitConvertBetweenTwoTintegers(int x, int y) {
  // XOR x and y to get the bit difference between x and y
  int z = x ^ y;
  return numberofBits(z);
}

public static int numberofBits(int x) {
  int n = 0;
  while (x != 0) {
    n = n + 1;
    // clear the least significant bit set
    x = x & (x - 1);
  }
  return n;
}