Structured Data

Structured variables are items that contain other data. Java has two kinds: objects (or classes) and arrays. An object contains data of various different kinds but an array contains multiple copies of just one kind of data, either simple or structured.
Most Java applications and applets contain objects and there is a large number of already existing classes that you may use in your programming.
From here you can study:
a) Arrays
b) Designing classes
c) Other objects
or
x) Exit to the Java foyer

Links:
Java ArrayLists and Arrays
Designing Classes
Some Object Types
Linked Lists
Time Analysis
Java Foyer