The Java TM Tutorial

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Trail: Learning the Java Language

## Lesson: Objects and Classes in Java

> In the lesson entitled Object-Oriented Programming Concepts you read about the concepts behind object-oriented programming. Now it's time to get to work and put those concepts to practical use in Java.

### A Brief Introduction to Classes

> To understand objects, you must understand classes. To understand classes, you need to understand objects. It's a circular process of learning. But you've got to begin somewhere. So, let's begin with two classes-- `Point` and `Rectangle`-- that are small and easy to understand. This section provides a brief discussion of these classes and introduces some important concepts and terminology.

### The Life Cycle of an Object

> Here, you will learn how to create a `Rectangle` object from the `Rectangle` class and use it. This section also discusses briefly how the system cleans up the object when it's no longer needed.

### Creating Classes

> This section provides a complete description of a larger class, `Stack`, and describes all of the components of a class that provide for the life cycle of an object created from it. It talks first about constructors, then about member variables and methods.

### Reality Break! The `Spot` Applet

> This is the last section of this lesson, and it contains the code for a fun little applet. Through that applet, you will learn how to subclass another class, how to implement an interface, and how to use an inner class to implement an adapter.

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