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Baldwin shows you how to extend an existing class to create a new class. The new class is the blueprint for a new type. This is the mechanism for class inheritance in Java. Inheritance provides a formal mechanism for code reuse.

Revised: Thu Mar 31 10:07:12 CDT 2016

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Table of contents

Preface

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

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Extending a class

This module shows you how to extend an existing class to create a new class. The new class is the blueprint for a new type.

Inheritance and code reuse

The existing class is often called the superclass and the new class is often called the subclass . This is the mechanism for class inheritance in Java. Inheritance provides a formal mechanism for code reuse.

The subclass inherits all of the variables and all of the methods defined in the superclass.

Although not explicitly demonstrated in this module, whenever you declare a reference variable whose type is defined by a class, that variable can be usedto store references to objects instantiated from that class or instantiated from any subclass of that class. Furthermore, that reference can be used to callmethods defined in or inherited into that class with no requirement for a cast. If the method is defined in that class and overridden in the subclass, and ifthe object is actually of the subclass type, the overridden version will be executed. This is polymorphism.

Car radios with tape players

A class from a previous module (whose objects represent car radios) is extended to define a new class, whose objects represent expanded car radios that contain tape players. (Yes, at one point in history, car radios did contain tape players instead of CDs.)

Sending messages to the object

Objects of the new class know how to respond to messages for inserting, playing, and removing a tape, in addition to those messages that are appropriate for objects of the original Radio class.

Discussion and sample code

The three pillars of OOP

In an earlier module, I explained that most books on OOP will tell you that in order to understand OOP, you must understand the following three concepts:

  • Encapsulation
  • Inheritance
  • Polymorphism

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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