converting an IP address to host name

Question

In my java application if user enters the IP we need to display the host name, if host name is given then we need to display the IP of the host.

For example if user

Answer 1

The project SomeKittens referred to you looks like a complete DNS server written in Java, which might be more than you need. Have a look at java.net.InetAddress:

java.net.InetAddress.getByName("example.com").getHostAddress();