Java Program to Check the Number is Prime or Not

Last Updated: 17 July, 2022

On this tutorial page we are going to learn how to write a Java program to check whether the number is prime or not.

A prime is a natural number that is greater than 1 and divided by 1 or itself only. If any number is divisible by any other number, then that number is not a prime number.

Prime Numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23 ...

Let's see the Java program implementation.

Program 1: Java Program to Check Prime Number using For Loop

  public class PrimeNumber {
    public static void main(String[] args) {
      isPrimeNumber(7);
      isPrimeNumber(16);
      isPrimeNumber(25);
      isPrimeNumber(29);
    }
  
    // method to check the number is prime or not
    static void isPrimeNumber(int number) {
      boolean isPrimeNumber = true;
  
      for (int i = 2; i <= number / 2; ++i) {
        // checking condition for non prime number
        if (number % i == 0) {
          isPrimeNumber = false;
          break;
        }
      }
  
      if (isPrimeNumber)
        System.out.println(number + " is a prime number.");
      else
        System.out.println(number + " is not a prime number.");
    }
  }

7 is a prime number.
16 is not a prime number.
25 is not a prime number.
29 is a prime number.

Program 2: Java Program to Check Prime Number using While Loop

  
  import java.util.Scanner;
  public class PrimeNumber {
    public static void main(String[] args) {
      
      Scanner scanner = new Scanner(System.in);
      System.out.print("Enter the number: ");
      int number = scanner.nextInt();
      scanner.close();
      
      boolean isPrimeNumber = true;
      int i = 2;
      
      while (i <= number / 2) {
        // checking condition for non prime number
        if (number % i == 0) {
          isPrimeNumber = false;
          break;
        }
        i++;
      }
      
      if (isPrimeNumber)
        System.out.println(number + " is a prime number.");
      else
        System.out.println(number + " is not a prime number.");
    }
  }