R7-33 First 50 Prime Numbers(JAVA)

Your program reads one natural numbers n in, and prints out the sum of the first n prime numbers starting from 2.

Input Format:

A positive whole numbers n, which is less than 103.

Output Format:

A number which is the sum of all the first n prime numbers.

Sample Input:

10

Sample Output:

129

 

import java.util.Scanner;


public class Main {
    public boolean is_prime(int n) {
        if(n < 2) return false;

        for (int i = 2; i * i <= n; i ++ )
            if(n % i == 0) return false;
        return true;
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int sum = 0;
        Main P = new Main();
        for (int i = 2, j = 0; j < n; i ++) {
            if(P.is_prime(i)) {
                sum += i;
                j ++ ;
            }
        }
        System.out.println(sum);
    }
}