Java用正则表达式判断IPv4合法性

import java.util.Scanner;

public class CheckIPAddress {

public static void main(String[] args) {

// TODO Auto-generated method stub

//String ip=\"192.168.1.1\";

Scanner scan=new Scanner(System.in);

System.out.println(\"请输入一个IP地址：\");

String IP=scan.next();

System.out.println(matches(IP));

}

public static String matches(String text)

{

if(text!=null&&!text.isEmpty())

{

String regex = \"(1\\\\d{2}|2[0-4]\\\\d|25[0-5]|[1-9]\\\\d|[1-9])\\\\.\"

+\"(1\\\\d{2}|2[0-4]\\\\d|25[0-5]|[1-9]\\\\d|\\\\d)\\\\.\"

+\"(1\\\\d{2}|2[0-4]\\\\d|25[0-5]|[1-9]\\\\d|\\\\d)\\\\.\"

+\"(1\\\\d{2}|2[0-4]\\\\d|25[0-5]|[1-9]\\\\d|\\\\d)$\";

if(text.matches(regex))

{

return text +\"\\n 是一个合法的IP地址\";

}else

{

return text +\"\\n 不是一个合法的IP地址\";

}

}

return \"请输入一个合法的IP地址\";

}

}