Concentrate on grasping the concept that the authors are trying to put through. Leave the specific packages / classes / APIs for later. Those are for later. For now, make sure you understand the following through and through(
in order):
a) Declarations, Access Control
b) Object oriented paradigm (what is encapsulation of data, abstraction, inheritance etc )
c) Flow Control(for loop, do while loop)
d) Exception handling in Java
e) Method overloading & overriding.
f)
String & Object classes
g) Collection Framework