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Baldwin explains the use of overloaded methods for the purpose of achieving compile-time polymorphism.

Revised: Thu Mar 31 11:22:34 CDT 2016

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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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  • Listing 1 . Definition of the class named A.
  • Listing 2 . Definition of the class named B.
  • Listing 3 . Definition of the driver class named Poly01.
  • Listing 4 . Complete program listing.


Previous modules introduced overloading and overriding methods. This module concentrates on the use of method overloading to achieve compile-time polymorphism .

Every class in Java is a direct or indirect subclass of the class named Object . Methods defined in the class named Object are inherited into all other classes. Inherited methods that are not declared final may be overridden to make their behavior more appropriate for objects instantiated from the new class.

Overloaded methods have the same name and different formal argument lists. They may or may not have the same return type.

Polymorphism manifests itself in Java in the form of multiple methods having the same name. This module concentrates on method overloading, sometimes referred to as compile-time polymorphism . Subsequent modules concentrate on method overriding, sometimes referred to as runtime polymorphism .

Overloaded methods may all be defined in the same class, or may be defined in different classes as long as those classes have a superclass-subclass relationship.

Discussion and sample code

Three concepts

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

I agree with that assessment.

Encapsulation and inheritance

Previous modules in this series have explained Encapsulation and Inheritance. This module will tackle the somewhat more complex topic of Polymorphism.

Overloading and overriding methods

In the modules on inheritance, you learned a little about overloading and overriding methods (you will learn more about these concepts as you progress through these modules) . This module concentrates on the use of overloaded methods to achieve compile-time polymorphism.

Real-world scenarios

The sample programs that I used in the previous modules in this series dealt with two kinds of car radios:

  • Plain car radios
  • Car radios having built-in tape players

I couched those programs in a real-world scenario in an attempt to convince you that encapsulation and inheritance really do have a place in the real world.

Questions & Answers

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Jyoti Reply
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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.
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I think
what is the stm
Brian Reply
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scanning tunneling microscope
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what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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Damian Reply
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Stoney Reply
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Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
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