Inheritance
• If we wanted to create a new class which was closely based on an
existing class, save for a few changes, we can easily accomplish this
with subclasses
• The nature of classes allow us to create subclasses which inherit all
the properties of the superclass (along with any additional
attributes/methods specific to the subclass).
• This OOP feature is called inheritance and is extremely useful when
creating large programs with many objects
Inheritance
• Consider the class Vehicle below:
public class Vehicle{
int engineSize;
String make;
int weight;
void Vehicle(int e, String m, int w){
// constructor
}
• I would like to create a subclass called Car which inherits all the
properties of Vehicle.
Inheritance
• We can accomplish this using the extends keyword:
public class Car extends Vehicle{
}
• Without further specification, the class Car has already inherited all
the properties of Vehicle
• Any new attributes/methods of Car will be unique only to Car (and
not visible to Vehicle)
Inheritance
• Recall that the constructor accepts as its parameters some values and
sets the attributes of the object to those values
• Creating a constructor method for the subclass requires us to:
1. Invoke the constructor from the superclass to set all inherited attributes
2. Set all non-inherited values in the subclass.
public class Car extends Vehicle{
private String owner;
super
public void Car(int e, String m, int w, String o ) {
keyword
super(e, s, w);
invokes the
this.owner = o;
constructor
from the
}
super class