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Learn through experimentation

I placed a print statement in each of the overloaded methods to display the type of that method's argument on the screen when the method is called. Byexamining the output, we can see that the method with the float parameter was called first (corresponding to the parameter of type int ). Then the method with the double parameter was called (corresponding to the parameter of type double ).

Converted int to float

Thus, the system selected the overloaded method requiring an incoming parameter of type float when the method was called passing an int as a parameter. The value of type int was automatically converted to type float .

In this case, it wasn't too important which method was called to process the parameter of type int , because the two methods do essentially the same thing -- compute and return the square of the incoming value.

However, if the behavior of the two methods were different from one another, it could make a lot of difference, which one gets called on an assignmentcompatible basis. (Even in this case, it makes some difference. As we will see later, when a very large int value is converted to a float , there is some loss in accuracy. However, when the same very large int value is converted to a double , there is no loss in accuracy.)

Avoiding the problem

One way to avoid this kind of subtle issue is to avoid passing assignment-compatible values to overloaded methods.

Passing assignment-compatible values to overloaded methods allows the system to resolve the issue through automatic type conversion. Automatic typeconversion doesn't always provide the best choice.

Using a cast to force your choice of method

Usually, you can cast the parameter values to a specific type before calling the method and force the system to select your overloaded method of choice.

For example, in this problem, you could force the method with the double parameter to handle the parameter of type int by using the following cast when the method named square is called:


However, as we will see later, casting may not be the solution in every case.

Back to Question 2

Answer 1

C. 9 17.64

Explanation 1

What is method overloading?

A rigorous definition of method overloading is very involved and won't be presented here. However, from a practical viewpoint, a method is overloaded whentwo or more methods having the same name and different formal argument lists are defined in the class from which an object is instantiated, or are inherited intoan object by way of superclasses of that class.

How does the compiler select among overloaded methods?

The exact manner in which the system determines which method to call in each particular case is also very involved. Basically, the system determineswhich of the overloaded methods to execute by matching the types of parameters passed to the method to the types of arguments defined in the formal argumentlist.

Assignment compatible matching

However, there are a number of subtle issues that arise, particularly when there isn't an exact match. In selecting the version of the method to call,Java supports the concept of an "assignment compatible" match (or possibly more than one assignment compatible match) .

Briefly, assignment compatibility means that it would be allowable to assign a value of the type that is passed as a parameter to a variable whose typematches the specified argument in the formal argument list.

Selecting the best match

According to Java Language Reference by Mark Grand,

"If more than one method is compatible with the given arguments, the method that most closely matches thegiven parameters is selected. If the compiler cannot select one of the methods as a better match than the others, the method selection process fails and thecompiler issues an error message."

Understanding subtleties

If you plan to be a Java programmer, you must have some understanding of the subtle issues involving overloaded methods, and therelationship between overloaded methods and overridden methods. Therefore, the programs in this module will provide some of that information and discuss someof the subtle issues that arise.

Even if you don't care about the subtle issues regarding method overloading, many of those issues really involve automatic typeconversion. You should study these questions to learn about the problems associated with automatic type conversion.

This program is straightforward

However, there isn't anything subtle about the program for Question 1 . This program defines two overloaded methods named square . One requires a single incoming parameter of type int . The other requires a single incoming parameter of type double . Each method calculates and returns the square of the incoming parameter.

The program calls a method named square twice in succession, and displays the values returned by those two invocations. In the first case, an int value is passed as a parameter. This causes the method with the formal argument list oftype int to be called.

In the second case, a double value is passed as a parameter. This causes the method with the formal argument list of type double to be called.

Overloaded methods may have different return types

Note in particular that the overloaded methods have different return types. One method returns its value as type int and the other returns its value as type double . This is reflected in the output format for the two return vales as shown below:

9 17.64

Back to Question 1


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..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
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.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
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
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
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.
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