package javaexercises.flowcontrol;

/**

* Write a program called HarmonicSum to compute the sum of a harmonic series,

* as shown below, where n=50000. The program shall compute the sum

* from left-to-right as well as from the right-to-left.

* Obtain the difference between these two sums and explain the difference.

*

* Harmonic(n) = 1 + 1/2 + 1/3 + ... 1/n

*/

/**

*

* @author User

*/

public class HarmonicSum {

public static void main(String[] args) {

int n = 50000;

HarmonicSum aHarmonicSum = new HarmonicSum();

double sumL2R = aHarmonicSum.printLeftToRightSum(n);

double sumR2L = aHarmonicSum.printRightToLeftSum(n);

System.out.printf("Difference: %.15f", (sumL2R - sumR2L));

System.out.println();

}

/**

* Left-to-right harmonic sum.

*

* @param int n

*/

private double printLeftToRightSum(int n)

{

double sum = 0.0;

for (int i = 1; i <= n; i++) {

sum += (double) 1/i;

}

System.out.printf("Left-to-right harmonic sum %.15f", sum);

System.out.println();

return sum;

}

private double printRightToLeftSum(int n)

{

double sum = 0.0;

for (int i = n; i >= 1; i--) {

sum += (double) 1/i;

}

System.out.printf("Right-to-left harmonic sum %.15f", sum);

System.out.println();

return sum;

}

}