Java tutorial
//package com.java2s; import java.util.regex.Pattern; public class Main { private static final String IPADDRESS_PATTERN = "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." + "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." + "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." + "([01]?\\d\\d?|2[0-4]\\d|25[0-5])$"; public static boolean validateIp(String ip) { Pattern ipVal = Pattern.compile(IPADDRESS_PATTERN); return ipVal.matcher(ip).matches(); } }