Inheritance
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Questions and Answers

What is the primary purpose of the main() method in a Java program?

  • To update the value of a private variable
  • To define the class variables
  • To declare the package visibility
  • To serve as the entry point for the program (correct)

    • What is the primary purpose of encapsulation in Java?

  • To make the data public
  • To hide the sensitive data from external users (correct)
  • To provide direct access to the class variables
  • To declare the class variables as private

    • What is the purpose of declaring class variables as private?

  • To make the data public
  • To declare the class variables as protected
  • To hide the sensitive data from external users (correct)
  • To provide direct access to the class variables

    • What is the default modifier for a class in Java?

    <p>Package-private</p> Signup and view all the answers

    What happens when a class is declared with the public modifier?

    <p>It can be accessed from any class</p> Signup and view all the answers

    What is the purpose of get and set methods in Java?

    <p>To provide public access to private variables</p> Signup and view all the answers

    What is the purpose of the protected modifier in Java?

    <p>To provide access to subclasses</p> Signup and view all the answers

    What is the correct syntax for accessing a class and its method from another package?

    <p>packagename.classname.methodname</p> Signup and view all the answers

    What type of relationship exists between a Bank and an Employee?

    <p>has-a</p> Signup and view all the answers

    When an Employee object is created, what happens to the Date object?

    <p>It is automatically referenced and used</p> Signup and view all the answers

    What is the type of relationship between a Triangle and a two-dimensional shape?

    <p>is-a</p> Signup and view all the answers

    What is the main difference between Aggregation and Composition?

    <p>Independence of the child object</p> Signup and view all the answers

    What happens when a car object is created?

    <p>It automatically references the engine object</p> Signup and view all the answers

    What is the relationship between a Programmer and an Employee?

    <p>is-a</p> Signup and view all the answers

    What is the characteristic of objects created from a subclass?

    <p>They have their own unique characteristics and also inherit properties of the superclass</p> Signup and view all the answers

    What is the purpose of inheritance in object-oriented programming?

    <p>To represent an is-a relationship between objects</p> Signup and view all the answers

    What is the primary concept of encapsulation in Object-Oriented Programming?

    <p>Hiding the data and showing the methods</p> Signup and view all the answers

    Which of the following is a feature of Object-Oriented Programming?

    <p>Inheritance</p> Signup and view all the answers

    What is the process of creating an object from a class?

    <p>Instantiation</p> Signup and view all the answers

    What is the purpose of a constructor in a class?

    <p>To initialize the class</p> Signup and view all the answers

    What is the concept of inheritance in Object-Oriented Programming?

    <p>Creating a new class from an existing class</p> Signup and view all the answers

    What is the main difference between procedural programming and object-oriented programming?

    <p>Procedural programming focuses on procedures, while object-oriented programming focuses on objects</p> Signup and view all the answers

    What is the concept of abstraction in Object-Oriented Programming?

    <p>Hiding the implementation details and showing the functionality</p> Signup and view all the answers

    What is the purpose of a package in Object-Oriented Programming?

    <p>To group related classes and interfaces together</p> Signup and view all the answers

    What is the main characteristic of a one-to-many association?

    <p>One object is related to multiple other objects.</p> Signup and view all the answers

    What does Java's multiple inheritance implement?

    <p>Association</p> Signup and view all the answers

    What type of relationship is characterized by a 'part-of' relationship?

    <p>Composition</p> Signup and view all the answers

    What is the main difference between composition and aggregation?

    <p>Composition is a strong association, while aggregation is a weak association.</p> Signup and view all the answers

    What is an example of a composition relationship?

    <p>A car has an engine.</p> Signup and view all the answers

    What type of association is characterized by a 'has-a' relationship?

    <p>Aggregation</p> Signup and view all the answers

    What is the main characteristic of a many-to-many association?

    <p>Multiple objects are related to multiple other objects.</p> Signup and view all the answers

    What is the direction of the association in aggregation?

    <p>Unidirectional</p> Signup and view all the answers

    What is the term for a subclass that inherits properties and behavior from a superclass?

    <p>Inheritance</p> Signup and view all the answers

    What is the purpose of the super() keyword in a subclass constructor?

    <p>To invoke a superclass constructor</p> Signup and view all the answers

    What is the correct order of method invocation in a subclass constructor?

    <p>Subclass constructor, superclass constructor</p> Signup and view all the answers

    What is the result of not using the super() keyword in a subclass constructor?

    <p>The superclass constructor will not be invoked</p> Signup and view all the answers

    What is the purpose of encapsulation in object-oriented programming?

    <p>To hide internal implementation details</p> Signup and view all the answers

    What is the correct syntax to invoke a superclass constructor with arguments?

    <p>super(arguments)</p> Signup and view all the answers

    What is the role of a superclass in inheritance?

    <p>To provide a template for the subclass</p> Signup and view all the answers

    When must the super() keyword be used in a subclass constructor?

    <p>As the first statement of the subclass constructor</p> Signup and view all the answers

    Study Notes

    Class Definition

    • A test class contains the main method, acting as the ignition key.
    • The source of this concept is Pearson (Liang).

    Encapsulation

    • A way to ensure that "sensitive" data is hidden from external users.
    • Achieved through:
      • Declaring class variables/attributes as private.
      • Providing public get and set methods to access and update the value of a private variable.

    Packages & Visibility Modifiers

    • Specify accessibility or visibility scope of a class and its data fields and methods.
    • Default modifier (Package-private or package access):
      • Accessible in the same package.
    • Public modifier:
      • Accessible from any class.
    • Private modifier:
      • Accessible only within the host class.
    • Protected modifier:
      • Not mentioned in the text.

    Association, Aggregation, and Composition

    • Association:
      • A relationship between two classes through their objects.
      • Types: one-one, one-to-many, and many-to-many.
      • Implements Java's multiple inheritance.
    • Aggregation:
      • A has-a relationship (e.g., a house has a door).
      • Unidirectional - one way (e.g., a student has a program).
    • Composition:
      • A class references objects of other classes as its members.
      • May be a part-of relationship (e.g., a car has an engine).
      • Strong/strict association (e.g., a car must have an engine to function).

    UML - Inheritance

    • Subclass extends superclass (e.g., Class Programmer extends Employee).
    • The keyword "super" is used to invoke the superclass constructor.

    The Keyword super in Inheritance

    • "super" invokes the no-arg constructor of its superclass.
    • "super(arguments)" invokes the superclass constructor that matches the arguments.
    • Must be the first statement of the subclass's constructor.

    OOP Concepts

    • Objectives:
      • Features of OO: encapsulation, polymorphism, abstraction, inheritance, and package.
    • Objects, Attributes, and Behaviors of Objects:
      • An object is an entity in real-life with distinct states (attributes) and behaviors (methods).
    • Association:
      • Dependency: child object can exist independently of the parent object.
      • Type of relationship: has-a or part-of.
      • Type of association: weak or strong.

    Inheritance

    • A form of is-a relationship (e.g., Programmer is an employee, salesrep is an employee, product manager is an employee).
    • Objects created from a subclass have their own unique characteristics but also inherit properties of the superclass.

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    Related Documents

    AC-S24-OOP-Lect03-Part1-Inheritance.pdf

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