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Baldwin concentrates on a discussion of the Java class. He shows you how to write a very simple program that simulates the manufacture and use of the car radio introduced in an earlier module.

Revised: Wed Mar 30 18:00:37 CDT 2016

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Table of contents

Preface

This module is the second in a collection of modules designed to teach you about the essence of Object-Oriented Programming (OOP) using Java.

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This module will concentrate primarily on a discussion of the Java class .

A simple Java program will be discussed to illustrate the definition and use of two different classes. Taken in combination, these two classes simulate the manufacture and the use of the car radio object discussed in an earlier module.

You will see how to write code to create a new Radio object by applying the new operator to the class named Radio . You will also see how to save that object's reference in a reference variable of type Radio .

You will see how to write code that is used to simulate the association of a radio button with a particular radio station.

You will see how to write code that is used to simulate the pressing of a radio button to play the radio station associated with that button.

You will see the definition of a class named Radio01 . This class consists simply of the main method. The main method of a Java application is executed by the Java Virtual Machine when the application is run. Thus, it is the driver for the entire application.

You will see the definition of a class named Radio . This class includes one instance variable and two instance methods.

(The instance variable is a reference variable that refers to a special kind of object that I refer to as an array object. I will provide a very brief discussion on array objects in this module. I will have more to say about array objects in a subsequent module.)

I will also provide a short discussion of class variables, which are not used in this program. I will explain that the use of class variables can often lead to undesirable side effects.

Finally, I will provide a very brief discussion of the syntax of a simple class definition in Java.

Discussion and sample code

What is a class?

I explained in an earlier module that a class is a plan from which many objects can be created. I likened the class definition to the plans from which millions of nearly identical car radios can be produced.

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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