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Listings

  • Listing 1 . Instantiating a new Radio object.
  • Listing 2 . Calling the playStation method.

Preview

Three important concepts

In order to understand OOP, you need to understand the following three concepts:

  • Encapsulation
  • Inheritance
  • Polymorphism

This module will concentrate on encapsulation. Encapsulation will be used as a springboard for a discussion of objects.

A description of an object-oriented program will be provided, along with a description of an object, and how it relates to encapsulation.

A car radio

I suspect that many of you grew up in a family where the family car contained a push-button radio and I also suspect that you learned how to operate thatradio. In fact, as children, many of you may have quarreled with your siblings about which button to push and which radio station to listen to.

In order to relate object-oriented programming to the real world, a car radio will be used to illustrate and discuss several aspects of software objects.

What you will learn

For example, you will learn that car radios, as well as software objects, have the ability to store data, along with the ability to modify or manipulatethat data.

You will learn that car radios, as well as software objects, have the ability to accept messages and to perform an action, modify their state, return a value, or some combination of the above.

You will learn some of the jargon used in OOP, including persistence, state, messages, methods, and behaviors.

You will learn where objects come from, and you will learn that a class is a set of plans that can be used to construct objects. You will learn that a Java object is an instance of a class.

You will see a little bit of Java code, used to create an object, and then to send a message to that object (call a method on the object) .

You will learn about Java references and reference variables. You will also learn a little about memory allocation for objects and variables in Java.

Discussion and sample code

Purpose of the miniseries

As mentioned earlier, I will describe and discuss the necessary and most significant aspects of OOP using Java.

The three pillars

Most books on OOP will tell you that in order to understand OOP, you need to understand the following three concepts:

  • Encapsulation
  • Inheritance
  • Polymorphism

I agree with that assessment.

Begin with encapsulation

Generally, speaking, these three concepts increase in difficulty going down the list from top to bottom. Therefore, I will begin with Encapsulation and work my way down the list in successive modules.

What is an Object-Oriented Program?

Many authors would answer this question something like the following:

An Object-Oriented Program consists of a group of cooperating objects, exchanging messages, for the purpose of achieving a common objective.

What is an object?

An object in OOP is a software construct that encapsulates data, (along with the ability to use or modify that data) , into a software entity.

What is encapsulation?

An interesting description of encapsulation was provided in an article by Rocky Lhotka regarding VB.NET. That description reads as follows:

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Source:  OpenStax, Accessible objected-oriented programming concepts for blind students using java. OpenStax CNX. Sep 01, 2014 Download for free at https://legacy.cnx.org/content/col11349/1.17
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