Object-Oriented Programming: Hierarchies and Interfaces
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Questions and Answers

What is a primary benefit of using superclasses?

  • It restricts editing privileges to the class owner only.
  • It helps avoid duplicating code. (correct)
  • It enables the creation of multiple instances of a class.
  • It allows easier debugging by maintaining multiple code fragments.

    • What must a class with one or more abstract methods also be declared as?

  • Static class
  • Concretized class
  • Final class
  • Abstract class (correct)

    • What is the role of the super keyword in a subclass?

  • It prevents access to the superclass methods.
  • It allows the subclass to inherit features of multiple superclasses.
  • It creates a new instance of the superclass.
  • It is used to call methods and constructors of the superclass. (correct)

    • What characterizes a concrete class?

    <p>It can create objects and supply its own constructor.</p> Signup and view all the answers

    What does polymorphism allow in relation to subclasses?

    <p>Subclasses can override features of the superclass and include unique traits.</p> Signup and view all the answers

    Which statement is true regarding abstract classes?

    <p>Abstract classes can contain concrete methods.</p> Signup and view all the answers

    What is the main purpose of interfaces in programming?

    <p>To define a contract for what a class can do without dictating how.</p> Signup and view all the answers

    What happens if you try to instantiate an abstract class?

    <p>It results in a compile-time error.</p> Signup and view all the answers

    Study Notes

    Hierarchies and Interfaces

    • Superclasses (Inheritance): Helps avoid duplicating code, making editing easier. Instead of editing multiple versions of the same code, only one version needs to be changed.

    • Abstract Classes: Used when a certain method should be empty or undefined. Declaring a method empty can cause issues; abstract keyword avoids this. A class containing abstract methods must also be abstract. Abstract classes cannot have objects instantiated.

    • Concrete Class: A class without abstract methods. It can create objects and supply its own methods, potentially inheriting from a superclass. Abstract and concrete classes can be mixed in a hierarchy, as long as all classes at the bottom of the hierarchy are concrete.

    • Calling Superclass Methods and Constructors: Use the super keyword to call superclass methods and constructors. When calling superclass constructors super() must be the first line in the subclass's constructor.

    • Polymorphism: Subclasses can have unique features and functionalities while also using those of the superclass. Subclasses can override methods of the superclass.

    • Interfaces: Enable a superclass to have multiple functionalities from different sources (without multiple inheritance). Interfaces' methods are undefined, do not have constructors nor other code. Another class can implement an interface by providing methods for each of the interface's traits. If the implementing class is abstract, it can leave some methods abstract. A class can implement multiple interfaces.

    Multiple Inheritance

    • Multiple Inheritance Limitations: A class cannot inherit directly from multiple classes; the solution is interfaces.

    • Interfaces: Enable a class to inherit code from multiple sources. Methods are undefined, have no constructors, and no other code.

    • Interface Implementation: Interfaces are abstract classes, all methods within the interface are undefined; classes that implement the interface must supply all the methods.

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    Description

    This quiz covers essential concepts in Object-Oriented Programming, specifically focusing on hierarchies and interfaces. Topics include superclasses, abstract classes, concrete classes, and polymorphism. Test your understanding of these fundamental programming principles and their applications.

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