编写一个程序HostLookup.java，完成主机域名与IP地址的查询：

(1)如果用户输入了域名，要求程序返回对应的IP地址

(2)如果用户输入了IP地址，要求程序返回其对应的域名

(3)编写一个方法，能够有效地检测输入的字符串是否是一个IP地址，并在HostLookup.java中调用验证。(Write a program HostLookup.java, complete the host domain name and IP address query:
(1) if the user enters the domain name, the program is requested to return the corresponding IP address
(2) if the user enters the IP address, the program is requested to return its corresponding domain name
(3) write a method that can effectively detect whether an input string is an IP address and call authentication in HostLookup.java.)