素数判断 Java

class Test{public static void main(String[] args) {boolean b=is_prime(13);}private static boolean is_prime(int i) {// TODO Auto-generated method stubif(i<=1)return false;int m = (int)(Math.sqrt(i)+0.5);for (int j = 2; j <=m; j++) {if(i%j == 0)return false;}return true;}}