问显示回文素数

EN

 import java.lang.Math;
public class PalindromicPrime {
    public static void main(String[] args) {
        int counter = 1;
        int start = 2;      

        isPalindrome(start);
        isPrime(start);

        while (counter <= 50) {
            if (isPrime(start) && isPalindrome(start)) {
                System.out.print(start + " ");
                if (counter % 10 == 0) {
                    System.out.println();
                    counter++;
                }
                start++;
            }
        }
    }
    public static boolean isPalindrome(int x) {
        int reverse = 0;
        while(x > 0) {
        reverse = reverse * 10 + x % 10;
        x = x / 10;
        }
        if (reverse == x) {
            return true;
        }
        else {
            return false;
        }       
    }
    public static boolean isPrime(int x) {
        if (x % 2 == 0 && x != 2) {
            return false;
        }

        int sqr = (int)Math.sqrt(x);
        for (int i = 3; i <= sqr; i += 2) {
            if(x % i == 0) {
                return false;
            }
        }
        return true;
    }

}