Question

How to get prime numbers using predefined methods in java?

Answer 1

/**
 * Simple Java program to print prime numbers from 1 to 100 or any number.
 * A prime number is a number which is greater than 1 and divisible
 * by either 1 or itself.
 */
public class PrimeNumberExample {

    public static void main(String args[]) {
     
     //get input till which prime number to be printed
      System.out.println("Enter the number till which prime number to be printed: ");
      int limit = new Scanner(System.in).nextInt();
   
      //printing primer numbers till the limit ( 1 to 100)
      System.out.println("Printing prime number from 1 to " + limit);
      for(int number = 2; number<=limit; number++){
          //print prime numbers only
          if(isPrime(number)){
              System.out.println(number);
          }
      }

    }

    /*
     * Prime number is not divisible by any number other than 1 and itself
     * @return true if number is prime
     */
    public static boolean isPrime(int number){
        for(int i=2; i<number; i++){
           if(number%i == 0){
               return false; //number is divisible so its not prime
           }
        }
        return true; //number is prime now
    }
}