Unit 9 Study • 5 min read

Inheritance

• idea of a class “inheriting” properties from another class

Ex:

• Vehicle Class
• A car is a type of vehicle
  • more of a “specialized vehicle”
• Bus
  • color could be a unique factor
• Train
  • Steam Engine Train
  • Diesel Engine Train
• you have a basic model that basic features such as engine, or color that all vehicles can inherit
• Constructors are not inherited!
  • Remember, constructors must be the name of the class, so if a constructor is “inherited”, its class and the constructor name will not be the same!
• they may have special features

Hiearchy is created in this example.

• Superclass will give everytrhing below in the hiearchy is refered to the subclass

Continued Example:

Class Vehicle:

• Name (String)
• make (String)
• model (String)
• Constructor: Vehicle (…)
• Method: moveForward()

Class Vehicle is the superclass of class Train

class Train:

• Name (String)
• make (String)
• model (String)
• Constructor: Train (…) //we would change this to Train instead of vehicle!
• Method: moveForward()

new addition:

• Conductor (String) //doesn’t carry to the vehicle class, conductor is a SUBCLASS of vehicle class
• moveFoward() method is still called the same thing, but we want to change the code inside it
  • this is called overwriting!
  • Overwriting: Changing the subclass body of a method that is inherited from a superclass

Class Train is the superclass of class DieselEngineTrain

class DieselEngineTrain:

• Name (String)
• make (String)
• model (String)
• Constructor: DiselEngineTrain: (…) //we would change this to DieselEngineTrain instead of Train!
• Method: moveForward() //inherit the overwritten method!
• Conductor (String)

new addition:

• oilLevel (double) //additional field added

//structure of example above

class Vehicle {
    public String name;
    public String make;
    public String model;

    public Vehicle(...) {
        //implentation not shown
    }
}

class Train extends Vehicle {
    public String conductor;

    public Train(...){
        //implenatation not shown
    }

    public void moveFoward(){
        //do something else
    }
}

class DieselEngineTrain extends Train {
    public double oilLevel;

    public DieselEngineTrain(...){
        //implementation not shown
    }
}

//super(params) --> accesses the superclass's constructor

|       public Vehicle(...) {

illegal start of type



|       public Vehicle(...) {

<identifier> expected

1. C
2. C
3. A
4. A
5. C
6. D
7. F
8. D
9. H //should be F

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