Java: Check if a number is Mersenne number or not

Java Numbers: Exercise-22 with Solution

Write a program to check if a number is a Mersenne number or not.

In mathematics, a Mersenne number is a number that can be written in the form M(n) = 2n − 1 for some integer n.
The first four Mersenne primes are 3, 7, 31, and 127

Test Data
Input a number: 127

Pictorial Presentation:

Java: Check if a number is Mersenne number or not.

Sample Solution:

Java Code:

import java.util.Scanner;
import java.math.BigInteger;
public class Example22 {

    public static void main(String args[])
        Scanner in = new Scanner(System.in);
        System.out.print("Input a number: ");
        int n = in.nextInt();
        int n1 = n + 1;

        int power = 0;
        int ans = 0;
        for(int i=0;;i++)
            else if(power==n1)
               System.out.println(n+" is a Mersenne number.");
   System.out.println(n+" is not a Mersenne number.");

Sample Output:

Input a number: 127                                                                                           
127 is a Mersenne number. 


Flowchart: Check if a number is Mersenne number or not

Java Code Editor:

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Java: Tips of the Day


Checks if a value is positive power of two.

To understand how it works let's assume we made a call IsPowerOfTwo(4).

As value is greater than 0, so right side of the && operator will be evaluated.

The result of (~value + 1) is equal to value itself. ~100 + 001 => 011 + 001 => 100. This is equal to value.

The result of (value & value) is value. 100 & 100 => 100.

This will value the expression to true as value is equal to value.

public static boolean isPowerOfTwo(final int value) {
    return value > 0 && ((value & (~value + 1)) == value);

Ref: https://bit.ly/3sA5d4I


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