Java tutorial
//package com.java2s; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main { public static boolean checkIPAddress(String ip) { Pattern pattern = Pattern.compile( "\\b((?!\\d\\d\\d)\\d+|1\\d\\d|2[0-4]\\d|25[0-5])\\.((?!\\d\\d\\d)\\d+|1\\d\\d|2[0-4]\\d|25[0-5])\\.((?!\\d\\d\\d)\\d+|1\\d\\d|2[0-4]\\d|25[0-5])\\.((?!\\d\\d\\d)\\d+|1\\d\\d|2[0-4]\\d|25[0-5])\\b"); Matcher matcher = pattern.matcher(ip); return matcher.matches(); } }