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Inheritance and Abstraction

1. Define the term inheritance

   • Inheritance is where a class uses the interface of another class (its attributes and methods), and optionally (re-)defines the behaviour of those methods. It may also add attributes or methods of its own.

2. Draw a diagram to show inheritance relationships between at least three things.

   •       Computer
           /   |   \
     Desktop Phone Laptop
             /   \
     Smartphone Flip-phone
     

3. Use the pseudocode below to answer the questions that follow:

   class Guitar
       private noOfStrings = 6
   
       public procedure holdFret()
           ...
       endprocedure
   
       public procedure strum()
           ...
       endprocedure
   endclass
   
   class ElectricGuitar inherits Guitar
       public procedure adjustVolume()
           ...
       endprocedure
   endclass
   

   1. Identify the parent class and the child class.

      • Parent: Guitar
      • Child: ElectricGuitar

   2. Identify the attributes and methods that ElectricGuitar inherits from Guitar

      • noOfStrings
      • holdFret()
      • strum()

4. Describe what happens when a class calls a super method.

   • When a class calls a 'super method', it calls the original method on its superclass (ignoring any overriden methods that the subclass may have), performing the original routine on the subclass object.

5. Explain the issue caused by allowing multiple inheritance.

   • The method resolution order is not immediately clear to inexperienced programmers.
   • Two classes with conflicting interfaces could be inherited from

6. Define the term abstract method, and explain when you might use one.

   • An abstract method is one for which the signature, but no implementation, is defined. Classes containing abstract methods may not be instantiated.
   • Abstract methods may be used when defining a base class that other classes will inherit from, but may not be instantiated, or when defining an interface for use by other classes

Code task

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