leetcode-go/medium/_468/Solution.java

package _468;

import java.util.regex.Pattern;

class Solution {
    public String validIPAddress(String IP) {
        Pattern ipv4 = Pattern.compile("^(25[0-5]|2[0-4]\\d|1\\d{2}|[1-9]\\d|\\d).(25[0-5]|2[0-4]\\d|1\\d{2}|[1-9]\\d|\\d).(25[0-5]|2[0-4]\\d|1\\d{2}|[1-9]\\d|\\d).(25[0-5]|2[0-4]\\d|1\\d{2}|[1-9]\\d|\\d)$");
        Pattern ipv6 = Pattern.compile("^[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}:[a-fA-F0-9]{1,4}$");
        boolean isV4 = ipv4.matcher(IP).matches();
        boolean isV6 = ipv6.matcher(IP).matches();
        if (isV4) {
            return "IPv4";
        } else if (isV6) {
            return "IPv6";
        }
        return "Neither";
    }

    private static void testValidIPAddress(String IP) {
        Solution solution = new Solution();
        System.out.println(solution.validIPAddress(IP));
    }

    public static void main(String[] args) {
        testValidIPAddress("172.16.254.1");
        testValidIPAddress("265.16.254.1");
        testValidIPAddress("0001:db8:85a3:0::8AFE:0370:7334");
    }
}