Here, try this:

import java.io.*;
class even_or_odd
{
static void check()throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
...

Well, yes, Java can be used to create such software...but it commands you to have in depth knowledge of how the Internet works.

Java can be used to even create a program on the lines of a 'packet...

What 'kind' of intrusion detection system do you want to develop? Java suits most types of development.