Prime number java

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Prime Number Java

A prime number is a number that is greater than one and divided by itself. Prime numbers are those numbers which cannot be divided by other numbers than 1 or itself.

Also read – palindrome number in java

Example : 2, 3, 5, 7, 11, 13, 17….

In the example for loop determines if given number is prime or not. In this for loop condition is checked if number is divisible by any number in range number / 2.

We set “temp” to true and break out of for loop. Hence it is a prime number. If number is not divisible “temp” is false and number is prime number.

Here’s java program to check whether a number is prime or not,

public class JavaPrimeNumber 
{
   public static void main(String[] args) 
   { 
      int number = 23;
      boolean temp = false;
      for(int a = 2; a <= number / 2; ++a)
      {
         // checking condition for non-prime number
         if(number % a == 0)
         {
            temp = true;
            break;
         }
      }

      if(!temp)
      {
         System.out.println(number + " is a prime number");
      }
      else
      {
         System.out.println(number + " is not a prime number");
      }
   }
}

Output :

23 is a prime number


Now let’s see java program to check prime number using a while loop,

import java.util.Scanner;

public class JavaPrimeNumber 
{
   public static void main(String[] args) 
   { 
      boolean checkPrime = false;
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter any number : "); 
      int number = sc.nextInt();
 
      int a = 2;
      while(a <= number / 2)
      {
         if(number % a == 0)
         {
            checkPrime = true;
            break;
         }
         ++a;
      }
 
      if(checkPrime)
      {
         System.out.println(number + " is a prime number.");
      }
      else
      {
         System.out.println(number + " is not a prime number.");
      }
      sc.close();
   }
}

Output:

Please enter any number : 50
50 is not a prime number.

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