题解 | #验证IP地址#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 验证IP地址
     * @param IP string字符串 一个IP地址字符串
     * @return string字符串
     */
    public String solve(String IP) {
        if (IP.contains(".")) {
            return isIPV4(IP);
        } else if (IP.contains(":")) {
            return isIPV6(IP);
        } else {
            return "Neither";
        }
    }

    /**
     * 判断是IPV4地址
     * 如：172.16.254.1
     */
    private String isIPV4(String ip) {
        String[] split = ip.split("\\.");
        if (split.length != 4) {
            return "Neither";
        }
        for (String s : split) {
            if (s.equals("") || (s.length() > 0 && s.startsWith("0"))) {
                return "Neither";
            }
            int i = 0;
            try {
                i = Integer.parseInt(s);
            } catch (NumberFormatException e) {
                return "Neither";
            }
            if (i < 0 || i > 255) {
                return "Neither";
            }
        }
        return "IPv4";
    }

    /**
     * 判断是IPV6地址
     * 如：2001:0db8:85a3:0:0:8A2E:0370:7334
     */
    private String isIPV6(String ip) {
        String[] split = ip.split(":");
        if (split.length != 8) {
            return "Neither";
        }
        if (ip.startsWith(":") || ip.endsWith(":")){
            return "Neither";
        }

        for (String s : split) {
            if (s.length() > 4 || s.length() == 0) {
                return "Neither";
            }
            final char[] chars = s.toCharArray();
            for (char ch : chars) {
                if (!((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'F') || (ch >= 'a' && ch <= 'f'))){
                    return "Neither";
                }
            }
        }

        return "IPv6";
    }
}