Java Program to Check Mersenne Number

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In the previous article, we have discussed Java Program to Check Cube Number

In this article we are going to understand what Mersenne number is and how we can check whether a number is Mersenne or not in Java with examples.

Program to Check Mersenne Number

Mersenne numbers are numbers which can be represented in the form of 2n-1.

Example :

  • 63: 63 =  64-1 :  26 – 1 Mersenne number
  • 7:    7  =  8 – 1 :  23 – 1 Mersenne number
  • 9:    9  =  23+1 :  Not a Mersenne number

In the above examples the number 63 and 7 are Mersenne numbers as they are one less than exponents of 2. However 9 is not a Mersenne number.

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Approach :

  1. Enter/declare a number and store it .
  2. We add 1 to the number and then check if it is a exponential form of 2.
  3. If a match is found then the number is said to be Mersenne number.

Program:

import java.util.Scanner;

public class MersenneNumber
{
    public static void main(String args[])
    {
        //Taking the number as input from the user using scanner class
        Scanner scan = new Scanner(System.in);
        System.out.print("Enter a number : ");
        int num = scan.nextInt();

        boolean flag = false;
        int temp = num+1,iter=1;
        // Loop runs until the equivalent power is found or
        // Until the exponent becomes greater than the number itself
        while(Math.pow(2,iter)<=temp)
        {
            // Checks whether there is some equivalent power of 2
            if(Math.pow(2,iter)==temp)
            {
                flag = true;
                break;
            }
            iter++;
        }

        if(flag)
        {
            System.out.println(num+" is a Mersenne number");
        }
        else
        {
            System.out.println(num+" is Not a Mersenne number");
        }
    }
}
Output:

Case-1

Enter a number : 63
63 is a Mersenne number

Case-2

Enter a number : 27
27 is Not a Mersenne number

Access the Simple Java program for Interview examples with output from our page and impress your interviewer panel with your coding skills.

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