I talk about about the most important classes and packages and lightly describe the rest of them. 

java.lang java.util  are the two main packages

java.lang.Object java.lang.Math java.lang.String 

java.awt.Graphics java.net.Socket for example.

I talk about java arrays, object serialization 

I talk about java assert keyword and AssertionException

I tell you about Remote Method Invocation

I explain what ports are in TCP/IP

and much more..