PROGRAM 12 : ENTER THE LOWER LIMIT AND UPPER LIMIT TO GET PAIRS OF TWIN PRIME NUMBERS.

Example:

 

 

PROGRAM:

 

 

import java.util.Scanner;
public class twinprime
{
    public static boolean isprime(int n) // CHECKS THAT THE NUMBER IS PRIME OR NOT
    {   int count = 0;
        for(int i = 1 ; i<=n ; i++)
        {  
            if(n%i==0)
               count++;
            }
        if(count==2)
          return true;
        else
          return false;
        }
       
    public static void main(String args[])
    {
        twinprime obj = new twinprime();
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter lower range:");
        int a = sc.nextInt();
        System.out.println("Enter upper range:");
        int b = sc.nextInt();
        if(a>b || a==b) // THE LOWER LIMIT CANNOT BE GREATER THAN UPPER LIMIT
           System.out.println("INVALID RANGE ENTERED.");
        else
        {
            System.out.println("The pairs of twin prime numbers in the following range are:");
            for(int i = a ; i<=b-2 ; i++)
            {
                if(obj.isprime(i)==true && obj.isprime(i+2)==true) // CONSECUTIVE NUMBERS CAN BE PRIME
                     System.out.println("(" + " " + i + " , " + (i+2) + " )");
                    }
                }
            }
        }