题解 | #合法IP#

使用REGEX matcher 和 pattern 解决这个问题

import java.util.*;
import java.util.regex.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String input = sc.nextLine();
            String validIpRegex = "^(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|[1-9])\\."
                    + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
                    + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
                    + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)$";
            //Matcher matcher = Pattern.compile("^(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|[1-9])\.(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)\.(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)\.(1\d{2}|2[0-4]\d|25[0-5]|[1-9]\d|\d)$").matcher(input);
            Pattern pattern = Pattern.compile(validIpRegex);
            Matcher matcher = pattern.matcher(input);
            if(matcher.find()){
                System.out.println("YES");
            }else{
                System.out.println("NO");
            }
        }

    }
}