题解 | #合法IP#

/*
 * Copyright (c) Huawei Technologies Co., Ltd. 2022-2022. All rights reserved.
 */

package com.nowcoder;

import java.util.Scanner;
import java.util.regex.Pattern;

/**
 * @author lushuifa
 * @version [版本号, 2022年05月05日}]
 * @ClassName : HJ90
 * @Description : IP合法性
 *
 * @since [2022-04-01]
 */
public class HJ90 {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 while 处理多个 case
        while (in.hasNext()) {
            boolean checkFlag = checkIp(in.nextLine());
            System.out.println(checkFlag?"YES":"NO");
        }
    }

    private static boolean checkIp(String inputString){
        String[] ipArray = inputString.split("\\.");
        if (ipArray.length!=4) {
            return Boolean.FALSE;
        }

        for (int i = 0; i < ipArray.length; i++) {
            if(null==ipArray[i] || ipArray[i].trim().equals("")){
                return Boolean.FALSE;
            }

            if(ipArray[i].length()>1&&ipArray[i].startsWith("0")){
                return Boolean.FALSE;
            }

            Pattern pattern = Pattern.compile("[0-9]*");
            // 判断每段都是数字
            boolean matchFlag = pattern.matcher(ipArray[i]).matches();
            if(!matchFlag){
                return Boolean.FALSE;
            }

            // 判断大小
            int subIp = Integer.parseInt(ipArray[i]);
            if(subIp<0 || subIp>255){
                return Boolean.FALSE;
            }
        }

        return Boolean.TRUE;
    }
}