Java: Check if a given number is Fibonacci number or not

Java Math Exercises: Exercise-27 with Solution

Write a Java program to check if a given number is a Fibonacci number or not.

Sample Solution:

Java Code:

import java.util.*;

class solution {
  static boolean isPerfectSquare(int x)
    {
       int s = (int) Math.sqrt(x); 
       return (s*s == x);
     }
  
   static boolean isFibonacci(int x)
      {
         return isPerfectSquare(5*x*x + 4) ||
           isPerfectSquare(5*x*x - 4);
     }

    public static void main(String[] args)
    {   
      Scanner scan = new Scanner(System.in);
      System.out.print("Input a number: ");
      int n = scan.nextInt();	       
	  if (n>0)
		{	
		 System.out.println("Is Fibonacci number? "+isFibonacci(n)); 
		}         
   }
}

Sample Output:

Input a number:  55
Is Fibonacci number? true

Flowchart:

Java Code Editor:

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