Java Program to Generate Harmonic Series

Harmonic series is the inverse of an arithmetic progression. In general, the terms in a harmonic progression can be denoted as

h1 = 1/a,  h2 = 1/(a+d), h3 = 1/(a+2d), h4 = 1/(a+3d), ……………..,  hn = 1/(a+nd).

Where h is the harmonic series, a is arithmetic progression and d is the common difference between arithmetic progression and n is the nth term.

Example 1: (Using while loop)

Java

// Java Program to Generate Harmonic Series

class HarmonicSeries {

    // this is a main function
    public static void main(String args[])
    {

        // num is the number of values we want in a series
        int num = 5;
        double result = 0.0;

        System.out.println("The harmonic series is: ");

        // printing the harmonic series till num value
        // using while loop
        while (num > 0) {

            // calculating harmonic values
            result = result + (double)1 / num;

            // after calculating harmonic value
            // decrementing num by 1 which means the common
            // difference is 1
            num--;
            System.out.print(result + ", ");
        }
    }
}

Output

The harmonic series is: 
0.2, 0.45, 0.7833333333333333, 1.2833333333333332, 2.283333333333333,

Time complexity: O(n) for given n terms

Auxiliary Space: O(1)

Example 2: (Using for loop)

Java

// Java Program to Generate Harmonic Series

class HarmonicSeries {

    // this is a main function
    public static void main(String args[])
    {

        // num is the number of values we want in a series
        int num = 5;
        double result = 0.0;

        System.out.println("The harmonic series is: ");

        // printing the harmonic series till num value
        // using for loop
        for (int i = num; i > 0; i--) {

            // calculating harmonic values
            result = result + (double)1 / i;
            System.out.print(result + ", ");
        }
    }
}

Output

The harmonic series is: 
0.2, 0.45, 0.7833333333333333, 1.2833333333333332, 2.283333333333333,

Example 3:

Java

// Java Program to Generate Harmonic Series

// importing necessary java packages
import java.util.Scanner;
import java.lang.*;

class HarmonicSeries {

    // this is a main function
    public static void main(String args[])
    {

        // scanner class is a pre-defined class in java
        // for taking input from keyboard
        Scanner in = new Scanner(System.in);

        System.out.print("Enter Number: ");

        // storing input value in num
        int num = in.nextInt();
        double result = 0.0;

        System.out.println("The harmonic series is: ");

        // printing the harmonic series till num value
        // using for loop
        for (int i = num; i > 0; i--) {

            // calculating harmonic values
            result = result + (double)1 / i;

            System.out.print(result + ", ");
        }
    }
}

Output

$ javac HarmonicSeries.java
$ java HarmonicSeries

Enter Number: 5
The harmonic series is: 
0.2, 0.45, 0.7833333333333333, 1.2833333333333332, 2.283333333333333

$ javac HarmonicSeries.java
$ java HarmonicSeries

Enter Number: 6
The harmonic series is: 
0.16666666666666666, 0.3666666666666667, 0.6166666666666667, 0.95, 1.45, 2.45

Time complexity: O(N) to generate series for given N terms

Auxiliary Space: O(1)