Java while loop find prime numbers

Question

We would like to display the first fifty prime numbers.

An integer greater than 1 is prime if its only positive divisor is 1 or itself.

For example, 2, 3, 5, and 7 are prime numbers, but 4, 6, 8, and 9 are not.

To test whether a number is prime, check whether it is divisible by 2, 3, 4, and so on up to number/2.

If a divisor is found, the number is not a prime. 

public class Main {
   public static void main(String[] args) {
      int NUMBER_OF_PRIMES = 50; // Number of primes to display

      int count = 0; // Count the number of prime numbers
      int number = 2; // A number to be tested for primeness

      System.out.println("The first 50 prime numbers are \n");

      //your code here
   }//from w ww . j  av a 2s  .  co  m
}





public class Main {
   public static void main(String[] args) {
      int NUMBER_OF_PRIMES = 50; // Number of primes to display

      int count = 0; // Count the number of prime numbers
      int number = 2; // A number to be tested for primeness

      System.out.println("The first 50 prime numbers are \n");

      // Repeatedly find prime numbers
      while (count < NUMBER_OF_PRIMES) {
         // Assume the number is prime
         boolean isPrime = true; // Is the current number prime?

         // Test if number is prime
         for (int divisor = 2; divisor <= number / 2; divisor++) {
            if (number % divisor == 0) { // If true, number is not prime
               isPrime = false; // Set isPrime to false
               break; // Exit the for loop
            }
         }
         // Print the prime number and increase the count
         if (isPrime) {
            count++; // Increase the count
            System.out.println(number);
         }
         // Check if the next number is prime
         number++;
      }
   }
}



PreviousNext

Related