HarmonicSum.java

public class HarmonicSum {
   public static void main(String[] args){
      // Define variables
      int maxDenominator = 50000;  // Use a more meaningful name instead of n
      double sumL2R = 0.0;         // Sum from left-to-right
      double sumR2L = 0.0;         // Sum from right-to-left
      double absDiff;              // Absolute difference between the two sums
   
      // for-loop for summing from left-to-right
      for (int denominator = 1; denominator <= maxDenominator; ++denominator) {
          // denominator = 1, 2, 3, 4, 5, ..., maxDenominator
          sumL2R += 1.0/(double) denominator;
          // Beware that int/int gives int, e.g., 1/2 gives 0.
      }
      System.out.println("The sum from left-to-right is: " + sumL2R);

      // for-loop for summing from right-to-left
      for (int denominator = maxDenominator; denominator >= 1; --denominator) {
         sumR2L += 1.0/(double) denominator;
      }
      System.out.println("The sum from right-to-left is: " + sumR2L);

      // Find the absolute difference and display
      if (sumL2R > sumR2L) {
         absDiff = sumL2R - sumR2L;
      }
      else {
         absDiff = sumR2L - sumL2R;
      }
      
      System.out.println("The absolute difference is: " + absDiff);
   }
}