Difference between method overriding and overloading

Is the concept of method overriding different from the concept of overloading. If so how they both differ.

Hi nancy,there is big difference between both:
see following example

When overriding, you change the method behavior for a derived class.
e.g Clas A
{
Virtual void hi(int a)
{
}
}

Class B:A
{
public overrid void hi(int a)
{

}
}

Overloading simply involves having a method with the same name within the class.

Example for Over loading

Class A
{
class a()

{

}
class a(int a)
{
}
}

Method overriding is a feature in Object Oriented programming language. This is used to implement a method for subclass which overrides in other words replaces the implementation of the super class. Overloading the concept of providing different meaning to a object based on the context of its presence. Overloading is one type of polymorphism and this is also a feature in Object Oriented programming language.

In overriding,
The method of a sub class takes priority over its counterpart in the super-class.

where as in Overloading,
2 or more methods with same name are available (have no priority over each other) but differ in their declaration and/or definition. Either of them may be executed depending on the number and/or type of arguments passed.

Any further clarifications? Feel free to ask :)

Overriding is the concept of having functions of same name and signature in different classes. one in the super class can be made virtual and other can override the functionality of virtual one.

Overloading is the concept of having functions of same name, but different signature in same class. They are differentiated by the compiler by their signatures.

Using overloading and overridding, you can acheive the concept of polymorphism.

Polymorphism means "one name, multiple forms". Using one name u can do multiple of actions...

Method overloading is a compile time polymorphism and Method Overridding is a runtime polymorphism...

Compile time polymorphism means compiler knows which object assigned to which class at the compiling time....Runtime polymorphism means compiler didn't know at the compile time, it only knows at a run time...

---------------------
suresh

methjod overloading means one method can callto diffrent sub class of base class and in method overriding method in subclass takes priority over it's counterpart.

Overloading methods
1.They appear in the same class or a subclass
2.They have the same name but, have different parameter lists, and can have different return types.
An example of an overloaded method is print() in the java.io.PrintStream class

Overriding methods
It allows a subclass to re-define a method it inherits from it's superclass
overriding methods:
1. It appears in subclasses
2. They have the same name as a superclass method
3. They have the same parameter list as a superclass method
4. They have the same return type as as a superclass method
5. They have the access modifier for the overriding method may not be more restrictive than the access modifier of the superclass method
·If the superclass method is public, the overriding method must be public
·If the superclass method is protected, the overriding method may be protected or public
·If the superclass method is package, the overriding method may be packagage, protected, or public
·If the superclass methods is private, it is not inherited and overriding is not an issue

What is overloading in java ?
In Java it is possible to define two or more methods within the same class that share the same name, as long as their parameter declarations are different. When this is the case,the methods are said to be overloaded, and the process is referred to as method
overloading. Method overloading is one of the ways that Java implements polymorphism.

What is Overriding in java ?
when a method in a subclass has the same name and type signature as a method in its superclass, then the method in the subclass is said to override the method in the superclass. When an overridden method is called from within a subclass, it will always refer to the version of that method defined by the subclass.

:) overlaoding:functions having same name and same signature.It is a run time polymorphism.Eg: virtual function
overlaoding:function having same name but different signature.It is a compile time polymorphism.Eg: operator overloading and function overloading.

method overloading is [B]designtime polymorphism [/B]whereas method overriding is [B]runtime polymorphism[/B]..
In overloading the parameters should be uniqe i.e the no of parameters shud differ or if same no of parameters r there the signature shud differ
why because the compiler should know the methods in complintime only.
whereas in overriding we reimplement or change the functionality of the base class method in derived class .the no of parameters & return type shud be same ..

Let me give one example.

METHOD OVERLOADING

class human(
{
void Hand(two paremeters){
Eating}
void Hand(three parameters) {
Writing }
void Hand(Five parameters) {
Fighting }

METHOD OVERIDING

class father {

void Hand(5 parameters){
Smoking;
}
}
class child extends father{
void Hand(5 parameters){
Drinking}
Thanks

[QUOTE=nancyphilips;1092]Is the concept of method overriding different from the concept of overloading. If so how they both differ.[/QUOTE]

OverLoading : when u want extend ur feature then u will use OverLoading.
OverRiding : When u dont want to use the existing feature then u will use OverRiding

Overriding method definitions
In a derived class, if you include a method definition that has the same name and exactly the same number and types of parameters as a method already defined in the base class, this new definition replaces the old definition of the method.

Explanation
A subclass inherits methods from a superclass. Sometimes, it is necessary for the subclass to modify the methods defined in the superclass. This is referred to as method overriding. The following example demonstrates method overriding.

Step 1
In this example we will define a base class called Circle

class Circle {

//declaring the instance variable
protected double radius;

public Circle(double radius) {
this.radius = radius;
}

// other method definitions here

public double getArea() {
return Math.PI*radius*radius;
}//this method returns the area of the circle

}// end of class circle

When the getArea method is invoked from an instance of the Circle class, the method returns the area of the circle.

Step 2
The next step is to define a subclass to override the getArea() method in the Circle class. The derived class will be the Cylinder class. The getArea() method in the Circle class computes the area of a circle, while the getArea method in the Cylinder class computes the surface area of a cylinder.

The Cylinder class is defined below.

class Cylinder extends Circle {

//declaring the instance variable
protected double length;

public Cylinder(double radius, double length) {
super(radius);
this.length = length;
}

// other method definitions here

public double getArea() { // method overriden here
return 2*super.getArea()+2*Math.PI*radius*length;
}//this method returns the cylinder surface area

}// end of class Cylinder

When the overriden method (getArea) is invoked for an object of the Cylinder class, the new definition of the method is called and not the old definition from the superclass(Circle).

Example code
This is the code to instantiate the above two classes

Circle myCircle;
myCircle = new Circle(1.20);

Cylinder myCylinder;
myCylinder = new Cylinder(1.20,2.50);

Please let me know if you need anything more

Some of the threads are merged for better management of the site.

MODERATOR

Overriding is the Functionality by witch a programmer can change the old functionality of any function even if he does`t know that what was the old one.
But in Overloading you have to change the parameter or the return type. this is the Conceptual difference

according to overriding:

mean - overriding the previous text with new text
accessing:

if u want to access this method from the super class to sub class that must be same return type and same method name.

example

class Superclass{
void display()
{
System.out.println("this is super class display");
}
}
class Subclass extends Superclass{
void display()
{
System.out.println("this is sub class display");
}
}
class Myclass{
public static void main(String args[])
{
subclass s=new subclass();
s.display();
}
output:
this is subclass display
explanation:
the subclass method display() simply overrided the method in superclass.

problems:these steps must be follow for overriding the method

-return type must be same
-access specifier must be same
-method name is equal in both classes.

according to overloading:

one name with different arguments and the return type may be any one.
overloading the methods in the same class possible.

example:
void display();
int display(int, int);
double display(double,double);

the one of the biggest difference ....method overriding is run time polymorphism where as method overloading is compile time polymorphism

In object oriented programming, Overloading is having the same method name with different signatures by which you can provide a different implementation for the same method name call.

Overriding has to do with inheritance super and sub class relationship. For overriding, method name and signatures should be same between the superclass and subclass. At runtime depending upon the object whether it is of superclass or subclass the functionality get called at provide different implementations.

Method overloading means "add" more behavior.
Method overriding means "Change" existing behavior.

[QUOTE=nancyphilips;1092]Is the concept of method overriding different from the concept of overloading. If so how they both differ.[/QUOTE]

[B]Function Overriding:[/B] In a child class, redefining the default behavior of an inherited function (default behavior of an inherited function is the behavior defined in the parent class for this function). For example,
class MyParent:
{
virtual Func() { print "Hello World"; }
};
class MyChild : public MyParent
{ // Default behavior of Func is (parent supplied) "Hello World"
//Redefining parent supplied behavior
Func() { Calculate equations; print equations;}
}
---------------------
[B]Function Overloading:[/B] Has nothing to do with inheritance. This is the ability that the programming language offers you, by which you can reuse the lable name of the function to perform different tasks at different times. For example:
class MyClass
{
int MyOLFunction () { print "Hello World"; return 0;}
int MyOLFunction (int x) { print "Hello World" x number of times; return 0;}
int MyOLFunction (char a) { print "Hello World"; print a; return 0;}

[B]//Note: The following are not function overriding, and will generate compile time error[/B]
long MyOLFunction () { print "Hello World"; return 0;} // Error
char MyOLFunction () { print "Hello World"; return 0;} // Error
};

Overriding means modifying or enhancing the method implementation in derived class.
Overloading means class have more than one method having same name but different implementation or different number of input parameters with different return type.

* Overloading deals with multiple methods in the same class with the same name but different signatures

* Overriding deals with two methods, one in a parent class and one in a child class, that have the same signature

* Overloading lets you define a similar operation in different ways for different data

* Overriding lets you define a similar operation in different ways for different object types

when ever we want code refinement(means some changes in method body) then that time we r using overloding

when ever we want cod replacement(means totally changes body) then that time we r useing overriding

i need the answer for the title

differences are as follows:
OVERLOADED OVERRIDING
1.)arguments- can change must not change

2.)exceptions-can change cant change except for covariant returns

3.)invocation-reference type determines which overloaded version is selected at compile time .the actual method tht is invoked is still svirtual method invocation that happens at runtime but the compiler will already know the signature of the method to be invoked .so at the runtime the argument match will already have been nailed down
but in overriding object type determines which methjod is selcted happens at runtime

I have one confusion..

If we have a method in superclass having signature [B]int abc(int a, int b)[/B]

and we also defined a method in the subclass having method signature [B]int abc(int c)[/B]
then what this phenomenon will be called. This is not overriding. Is this method overloading for subclass.

any help will be appreciable..:)

Hi there... PPPreeti :-) ... Yes, this is called Function Overloading.

Overriding is the process of "redefining" the behavior of a parent class' method in the child class.
Overloading is the process of "creating" a new method with a lable that is already existing within the "scope" of the method.

As you may already be aware, a function or method is identified by its entire signature - not just its lable name. Lable ("abc" in your example) is only a part of the entire signature.

Therefore, when you change the signature and keep the lable name intact within a given scope, then you are overloading - regardless of whether you are doing it in a parent or child class. When you are keeping the entire signature (including the lable) intact and rewriting just the body of the function (or behavior of a method) within a child class, then you are overriding the pre-defined (or parent's) behavior of the method.

In your example, what you are doing is - "creating" a brand new signature. It so happens that one of the components that make up this signature (the lable name) is also used in a different signature (parent class' method) within the same scope.

By the way, overriding or overloading of a function occurs within the same scope of that function. If done outside the scope, it's neither overloading nor overriding. Say for example, there is a class MyClass with a function func1

class MyClass {
public:
void func1 (int a, int b)
{ for (int i =0; i++ < a; cout << b); }

};

and I define another function in a whole different class or even in a main() as
void func1 (int a, int b) { for (int i =0; i++ < a; cout << b); }

this is neither overriding (no way related to class MyClass) nor overloading (not within the scope of MyClass::func1 - so no conflict).


And a couple more things...
1. For overriding to work, the parent method must be virtual.
2. For overloading to work, the signature must change, not just the return type. Return type is not a part of the function signature. Whether the return type changes or not does not matter.

Does it confuse you further???

--Som G

[QUOTE=pppreeti;58288]I have one confusion..

If we have a method in superclass having signature [B]int abc(int a, int b)[/B]

and we also defined a method in the subclass having method signature [B]int abc(int c)[/B]
then what this phenomenon will be called. This is not overriding. Is this method overloading for subclass.

any help will be appreciable..:)[/QUOTE]

In java,c++ there are two type of polymorphism: compile time polymorphism (overloading) and runtime polymorphism (overriding).

When you override methods, JVM determines the proper methods to call at the program’s run time, not at the compile time. Overriding occurs when a class method has the same name and signature as a method in parent class.

Overloading occurs when several methods have same names with

* Overloading is determined at the compile time.
* Different method signature and different number or type of parameters.
* Same method signature but different number of parameters.
* Same method signature and same number of parameters but of different type


Example of Overloading
int add(int a,int b)
float add(float a,int b)
float add(int a ,float b)
void add(float a)
int add(int a)
void add(int a) //error conflict with the method int add(int a)

Example: Overloading


Class BookDetails{
String title;
String publisher;
float price;

setBook(String title){
}
setBook(String title, String publisher){
}
setBook(String title, String publisher,float price){
}


}

Example: Overriding

class BookDetails{
String title;

setBook(String title){ }
}

class ScienceBook extends BookDetails{

setBook(String title){} //overriding

setBook(String title, String publisher,float price){ } //overloading

}

Overriding - same method names with same arguments and same return types associated in a class and its subclass.

Overloading - same method name with different arguments, may or may not be same return type written in the same class itself.

_____________________________
Cegonsoft

if the super class and sub class have the same name and signature then this is called METHOD OVERRIDING.

Method overriding and overloading is the different types of polymorphism.
Method overloading is compile time polymorphism. In overloading function name is same but signature is different.we can say that return type & parameter list should be different.
Method overriding is runtime polymorphism. In overriding function name & signature are same.It is implemented using virtual & override kyword

[QUOTE=sudhansulenka;12391]:) overlaoding:functions having same name and same signature.It is a run time polymorphism.Eg: virtual function
overlaoding:function having same name but different signature.It is a compile time polymorphism.Eg: operator overloading and function overloading.[/QUOTE]

In the above explanation, u wrote function overloading. While any1 is function overriding.
So, pls correct the error where function overloading will come and where function overriding.