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Learn about abstract methods, abstract classes, and overridden methods. You will also learn about overriding the toString method.

Revised: Sat Apr 02 20:33:36 CDT 2016

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Table of contents

Preface

This module is one of a series of modules designed to teach you about Object-Oriented Programming (OOP) using Java.

Viewing tip

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the Figures and Listings while you are reading about them.

Figures

  • Figure 1 . Program output on the command line screen.
  • Figure 2 . Default behavior of the toString method.
  • Figure 3 . More on the default behavior of the toString method.

Listings

  • Listing 1 . Source code for class Prob04.
  • Listing 2 . Beginning of the class named Prob04MyClass.
  • Listing 3 . Override the abstract getData method.
  • Listing 4 . Override the toString method.
  • Listing 5 . Complete program listing.

Preview

The program that I will explain in this module produces no graphics and does not require the use of Ericson's media library.

OOP concepts

The program illustrates the following OOP concepts:

  • Extending an abstract class.
  • Parameterized constructor.
  • Defining an abstract method in the superclass and overriding it in a subclass.
  • Overridden toString method.

Program specifications

Write a program named Prob04 that uses the class definition shown in Listing 1 to produce the output on the command-line screen shown in Figure 1 .

Figure 1 . Program output on the command line screen.
Prob04 DickBaldwin 9595

Pseudo random data

Because the program generates and uses a pseudo random data value each time it is run, the actual values displayed in the last two lines of Figure 1 will differ from one run to the next. However, in all cases, the two values must match.

New classes

You may define new classes as necessary to cause your program to behave as required, but you may not modify the class definition for the class named Prob04 given below.

Discussion and sample code

Will explain in fragments

I will explain this program in fragments. A complete listing is provided in Listing 5 near the end of the module.

I will begin with the driver class named Prob04 , which is shown in its entirety in Listing 1 .

Listing 1 . Source code for class Prob04.
import java.util.*; abstract class Prob04{public static void main(String[] args){Random generator = new Random(new Date().getTime()); int randomNumber = (byte)generator.nextInt();Prob04 objRef = new Prob04MyClass(randomNumber);System.out.println(objRef); System.out.println(objRef.getData());System.out.println(randomNumber); }//end main//Declare the signature of an abstract class. public abstract int getData();}//end class Prob04

The import directive

The import directive at the beginning of Listing 1 is required because the program requires access to the Random class and the Date class, both of which are defined in the java.util package.

Questions & Answers

what does preconceived mean
sammie Reply
physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
Wekolamo Reply
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Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
Manix Reply
Agreed 👍 There are many parts of our brains and behaviors, we really need to get to know. Blessings for everyone and happy Sunday!
ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
Zyryn Reply
good👍
Jonathan
and having a good philosophy of the world is like a sandwich and a peanut butter 👍
Jonathan
generally amnesi how long yrs memory loss
Kelu Reply
interpersonal relationships
Abdulfatai Reply
What would be the best educational aid(s) for gifted kids/savants?
Heidi Reply
treat them normal, if they want help then give them. that will make everyone happy
Saurabh
What are the treatment for autism?
Magret Reply
hello. autism is a umbrella term. autistic kids have different disorder overlapping. for example. a kid may show symptoms of ADHD and also learning disabilities. before treatment please make sure the kid doesn't have physical disabilities like hearing..vision..speech problem. sometimes these
Jharna
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Jharna
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Jharna
results you'll get.. please consult a therapist to know what suits best on your child. and last as a parent. I know sometimes it's overwhelming to guide a special kid. but trust the process and be strong and patient as a parent.
Jharna
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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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