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Leytton:网上好多错的，亲测留着备用

import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class IsIp {

	public static void main(String[] args) {
		System.out.println(isboolIp(""));
		System.out.println(isboolIp("192.168.1.1"));
		System.out.println(isboolIp("256.2.3.4"));
		System.out.println(isboolIp("1.2.3.4"));
		System.out.println(isboolIp("1.2.3.4.5"));
		System.out.println(isboolIp("1.2.3.4."));
	}
	
	/** * 判断是否为合法IP * @return the ip */
    public static boolean isboolIp(String ipAddress) {
        String ip = "([1-9]|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5])(\\.(\\d|[1-9]\\d|1\\d{2}|2[0-4]\\d|25[0-5])){3}"; 
        Pattern pattern = Pattern.compile(ip);
        Matcher matcher = pattern.matcher(ipAddress);
        return matcher.matches();
    }
}