Question

In Java: The n^th Harmonic number is the sum of the reciprocals of the first n natural numbers:
H(n) = 1+ 1/2 + 1/3 +1/4 +... +1/n

Write a recursive method and an accompanying main method to compute the n^th Harmonic number.

I have tried but get a blank and would really apreciate a fully explained code.

Answer 1

<Harmonic.java>

import java.io.*;

public class Harmonic {

public static double harmonic(int n) { // create a double type method
    if(n == 1) {
        return 1.0;                    
    } else {
        return (1.0 / n) + harmonic(n - 1); //using recursion method to calculate every next 
                                            //value for harmonnic number & adding them all.
    }
}

public static void main(String [] args) throws IOException {

double result;

System.out.print("Enter the value of n : "); //user input for the limit of n value

BufferedReader inp = new BufferedReader (new InputStreamReader(System.in));

String s= inp.readLine();

int x = Integer.parseInt(s);

Harmonic h = new Harmonic(); //create an object of the Harmonic class which we defined above.

result = h.harmonic(x); //using this object, call the harmonic() method defined inside Class.

System.out.print("The value of nth harmonic number is : " + result); //print the nth harmonic number value.

}

}