Java编程题：输入ip地址，验证是否正确

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner input = new Scanner(System.in);
        while (input.hasNext()) {
            boolean flag = true;
            String s = input.nextLine();
            String a[] = s.split("\.");
            if (s.equals("q")){
                break;
            }
            if (s.length() < 7 || s.length() > 15 || a.length != 4 ) {
                System.out.println("N");
                continue;
            }
            for (int i = 0; i < a.length; i++) {
                if (!a[i].matches("[0-9]{1,3}")) {
                    flag = false;
                    break;
                }
                if (Integer.valueOf(a[i]) >= 0 && Integer.valueOf(a[i]) <= 255) {
                    flag = true;
                } else{
                    flag = false;
                    break;
                }
            }
            if (flag)
                System.out.println("T");
            else
                System.out.println("N");
        }
        input.close();
    }
}