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) {
        // write code here
        if (isIpv4(IP))
            return "IPv4";
        else if (isIpv6(IP))
            return "IPv6";
        return "Neither";
    }
    public  boolean isIpv4(String IP) {
        try {
            if (IP == null || "".equals(IP)) {
                return false;
            }
            String[] ipv4Array = IP.split("\\.");
            if (ipv4Array.length != 4) {
                return false;
            }
            for (int i = 0; i < ipv4Array.length; i++) {
                int parseInt = Integer.parseInt(ipv4Array[i]);
                if (parseInt > 255) {
                    return false;
                }
                //不是零开头
                if (!ipv4Array[i].equals(String.valueOf(parseInt))) {
                    return false;
                }

            }
            return true;
        } catch (NumberFormatException e) {
            return false;
        }

    }

    public  boolean isIpv6(String IP) {
        try {
            if (IP == null || "".equals(IP)) {
                return false;
            }
            if (IP.indexOf("::") > 0) {
                return false;
            }
            //这个IP.split(":",-1); 坑死我了，我一直写的是IP.split(":");
            String[] ipv6Array = IP.split("\\:",-1);
            if (ipv6Array.length != 8) {
                return false;
            }

            for (int i = 0; i < ipv6Array.length; i++) {
                if (ipv6Array[i].length() > 4 || ipv6Array[i].length() == 0) {
                    return false;
                }
                
                if (!isValidString(ipv6Array[i])) {
                    return false;
                }

            }
            return true;
        } catch (NumberFormatException e) {
            return false;
        }

    }
    public  boolean isValidString(String input) {
        return !input.isEmpty() && input.matches("[0-9A-Fa-f]+");
    }
}