1
Introduction to Programming
with Java, for Beginners
Polymorphism
- Overloading
- Overriding
More overriding (inheritance)
CIS110 1
Polymorphism
Polymorphism means many (poly) shapes (morph)
In Java, polymorphism refers to the fact that you can have
multiple methods with the same name in the same class
There are two kinds of polymorphism:
Overloading
¾Two or more methods with different signatures
Overriding
¾A method in a subclass to “override” a method in the superclass
that has the same signature
We’ve already seen Overloading scenario with Constructors
E.g. public RealVector(double x, double y) {..}
public RealVector(double mag, Angle theta) {..}
CIS110 2
Method Overloading
Method overloading occurs when
A class has two or more methods with the same name but
different signatures
¾Different signature -> the number, order, or types of their
parameters differ
// the foo method is overloaded
public void foo() {.. }
public void foo(int x) { ..}
public void foo(int x, double y) {..}
When the foo(..) method is called, Java picks the one that
“matches”. E.g.
foo(10, 350.5);
CIS110 3
Overriding
Overriding occurs if
There are two or more methods with the same
name and the same signature in an inheritance
chain
For example, the Object class has a toString()
method
¾It can be overriden in a subclass simply by creating a
method with the same signature
public String toString() {. .}
Java picks the “lowest” method in the inheritance
chain possible
