1. Lecture 9_1 George Koutsogiannakis
CS 116
Lecture 9_1
George Koutsogiannakis

2. TOPIC
Method Overriding
Method Overloading

3. Method Overriding
Sometimes the same method is used to produce two different results in two different classes i.e:
Assume that method m is in super class A and it has signature:
public int m(double d) { method code to produce a task}
Suppose that class B is sub class of A (inherits A). As a result it has inherited the method m of A also.
Suppose that class B is interested in adding code to m (and thus modify the original code) but it wants the same signature as m (same name, same returned value, same arguments).
B can go ahead and modify the method m which is different than the m of the super class. This is called method overriding i.e

4. Method Overriding i.e. Class B version of m: public int m(double d1) {
int x = super.m(3.4);
// the above is a call to the A class version to get its code
//Add additional code here i.e.
int y=(int)(d1+x);
return y; }

5. Method Overriding
The client class will go ahead and access m with an object of B:
B b=new B();
int i= b.m(5.0);

6. Method Overloading
Method overloading happens when a class decides to create a second version of a method that exists in the same class but with different list of arguments i.e.
In our previous example the lass A had the method m with signature:
public int m(double d) { method code to produce a task}
Class A also decides that it wants to have different versions of m but this time the signature will also be affected by the fact that the list of argument is different i.e.
public int m(double d, String str) { method code to produce a slightly different task}
This is called method overloading (notice that both versions of m exist in the same class A)

7. Method Overloading
The user of class A decides which version of m wants to use simple by indicating the arguments in m i.e.
A a= new A();
int x=a.m(2.4);
int y=a.m(3.4, “a string”);
An good example of method overloading is the different constructors in a class!