# Java Program to Check Twin Prime Number

## Program to Check Twin Prime Number

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

Twin Primes are prime numbers which are prime number that is either 2 less or 2 more than another prime number.

 Example :

(41,43) Twin Prime number
(67,60 )Not Twin Prime number
(99,33 ) Not Twin Prime number

In the above examples the numbers 41,43 are only twin primes. In the second set 60 is not a prime number and in the third 33 is not a prime number. Hence they are not twin primes.

Let’s see different ways to check twin prime number.

Approach :

1. Enter/declare two numbers and store them in num1 and num2.
2. Then, we check if both the numbers are prime numbers and the absolute difference between them is 2.

### Method-1: By Using Static Value

import java.util.Scanner;

{
public static void main(String args[])
{
//first number declared
int num1 = 41;
//second number declared
int num2 =43;

//Logic to check for coprimes
if (prime(num1) && prime(num2) && (Math.abs(num1 - num2) == 2))
{
System.out.println(num1+" and "+num2+" are Twin Primes");
}
else
{
System.out.println(num1+" and "+num2+" are Not Twin Primes");
}
}

//Function to check for prime
static boolean prime(int num)
{
int iter = 2;
boolean flag = true;
while (num > iter)
{
if (num % iter == 0)
{
flag = false;
break;
}
iter++;
}
return flag;
}
}

Output:

41 and 43 are Twin Primes

### Method-2: By User Input Value

import java.util.Scanner;

{
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 first number : ");
int num1 = scan.nextInt();
System.out.print("Enter second number : ");
int num2 = scan.nextInt();

//Logic to check for coprimes
if (prime(num1) && prime(num2) && (Math.abs(num1 - num2) == 2))
{
System.out.println(num1+" and "+num2+" are Twin Primes");
}
else
{
System.out.println(num1+" and "+num2+" are Not Twin Primes");
}
}

//Function to check for prime
static boolean prime(int num)
{
int iter = 2;
boolean flag = true;
while (num > iter)
{
if (num % iter == 0)
{
flag = false;
break;
}
iter++;
}
return flag;
}
}

Output:

Case-1

Enter first number : 41
Enter second number : 43
41 and 43 are Twin Primes

Case-2

Enter first number : 41
Enter second number : 47
41 and 47 are Not Twin Primes