2 Methods to find Prime Number in Java

Prime numbers are the numbers that are divided by 1 or the number itself and cannot be divided by any other number without leaving the remainder.

For example, 17 is a prime number. It is only divided by 1 and cannot be divided by any other number with the remainder of 0.

Here we have 2 methods to check whether a given number is prime or not:

import java.util.Scanner;
 public class Main
 {
  public static void main(String[] args)
  {
  //Take input from the user
  //Create instance of the Scanner class
  Scanner sc = new Scanner(System.in);
  System.out.println("Enter a number : ");
  int num = sc.nextInt();
  int flag=0;
  int i, temp=num/2;
  if(num==0||num==1)
  {
  System.out.println(num+" is not prime number");
  }
  else
  {
  for(i=2;i<=temp;i++)
  {
  if(num%i==0)
  {
  System.out.println(num+" is not a prime number");
  flag=1;
  break;
  }
  }
  if(flag==0)
  {
  System.out.println(num+" is a prime number");
  }
  }//end of else
  }
 }

Output:

import java.util.Scanner;
 public class Main
 {
  static int i=2;
  public static void main(String[] args)
  {
  //Take input from the user
  //Create instance of the Scanner class
  Scanner sc = new Scanner(System.in);
  System.out.println("Enter the number: ");
  int num = sc.nextInt();
 
  if (checkPrime(num))
  {
  System.out.print(num+" is a prime number ");
  }
  else
  {
  System.out.println(num+" is not a prime number ");
  }
 
  }
  static boolean checkPrime(int num)
  {
  // Corner cases
  if (num == 0 || num == 1)
  {
  return false;
  }
  // Checking Prime
  if (num == i)
  return true;
  // Base cases
  if (num % i == 0)
  {
  return false;
 
  }
  i++;
  return checkPrime(num);
  }
 }

Output:

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