code: private int hammingDistance(BinarySolution solutionOne, BinarySolution solutionTwo) {
      int distance = 0;
      for (int i = 0; i < problem.getNumberOfVariables(); i++) {
        distance += hammingDistance(solutionOne.getVariableValue(i), solutionTwo.getVariableValue(i));
      }
  
      return distance;
    }
docs: Calculate the hamming distance between two solutions
  
  @param solutionOne A <code>Solution</code>
  @param solutionTwo A <code>Solution</code>
  @return the hamming distance between solutions