Programming Languages 1 - Lecture 5
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Questions and Answers

What is the name of the first class defined?

Product

What is the name of the second class defined that extends the "Product" class?

Toy

What is the purpose of the "super(n,p)" statement in the "Toy" class constructor?

  • It defines the tax rate for "Toy" objects.
  • It overrides the "print()" method of the "Product" class.
  • It initializes the "age" attribute of the "Toy" object.
  • It calls the constructor of the parent class, "Product", to initialize the "name" and "price" attributes. (correct)

    • How many methods are defined in the "Product" class?

    <p>2</p> Signup and view all the answers

    How many methods are defined in the "Toy" class?

    <p>3</p> Signup and view all the answers

    What is the return type of the "tax()" method in the "Toy" class?

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

    The "print()" method of the "Toy" class overrides the "print()" method of the "Product" class.

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

    The "Product" class is an abstract class.

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

    The "Toy" class is an abstract class.

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

    What is the inheritance relationship between the "Toy" class and the "Product" class?

    <p>The Toy class inherits from the Product class.</p> Signup and view all the answers

    The "Product" class contains a default constructor. What is its purpose?

    <p>The &quot;Product&quot; class contains a default constructor. It provides a way to create an instance of the &quot;Product&quot; class without initializing any attributes. The constructor would be called with no arguments.</p> Signup and view all the answers

    The "Product" class contains a parameterized constructor. What is its purpose?

    <p>The &quot;Product&quot; class contains a parameterized constructor. It provides a way to create an instance of the &quot;Product&quot; class and sets initial values for the &quot;name&quot; and &quot;price&quot; attributes of the object.</p> Signup and view all the answers

    The "Toy" class contains a parameterized constructor. What is its purpose?

    <p>The &quot;Toy&quot; class contains a parameterized constructor. It provides a way to create an instance of the &quot;Toy&quot; class and sets initial values for the &quot;name&quot;, &quot;price&quot;, and &quot;age&quot; attributes of the object while calling the parent class constructor to initialize name and price.</p> Signup and view all the answers

    How is Polymorphism used in Java?

    <p>Polymorphism means &quot;many forms.&quot; In Java, it allows an object to take on multiple forms, either through method overriding (at runtime) or method overloading (at compile time).</p> Signup and view all the answers

    Overloading methods in Java is an example of static polymorphism (compile-time polymorphism).

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

    Overriding methods in Java is an example of dynamic polymorphism (runtime polymorphism).

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

    What is the difference between method overloading and method overriding in Java?

    <p>Method overloading refers to having multiple methods with the same name but different parameters in the same class. Method overriding, on the other hand, involves a subclass providing a new implementation for a method inherited from its parent class. Overloading takes place within a single class but overriding occurs across classes (parent and child). Overloading is resolved at compile time, while overriding is resolved at runtime.</p> Signup and view all the answers

    The term "Upcasting" refers to converting an object of a child class to its parent class using a reference variable.

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

    The term "Downcasting", refers to converting an object of the parent class to its child class using a reference variable.

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

    If you have an object of type "Circle" and a reference variable of type "Shape", then assigning the "Circle" object to the "Shape" reference variable is an example of Upcasting.

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

    What is the main purpose of the "getClass()" method in Java?

    <p>The &quot;getClass()&quot; method in Java is used to dynamically determine the actual type of an object at runtime. It is essential for achieving runtime polymorphism by allowing code to respond differently based on the specific type of an object, enabling more dynamic and adaptable behavior.</p> Signup and view all the answers

    All classes in Java are directly or indirectly derived from the "Object" class.

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

    What is the main principle of abstraction in Java?

    <p>The main principle of abstraction in Java is to focus on the essential characteristics of an object and hide the underlying implementation details, exposing only the necessary information to the user. This promotes code reusability, flexibility, and easier maintenance.</p> Signup and view all the answers

    Which of these is NOT a characteristic of an abstract class?

    <p>Abstract classes can be instantiated.</p> Signup and view all the answers

    An abstract method only has a declaration and no implementation.

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

    A class can be declared as abstract even without containing any abstract methods.

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

    Study Notes

    Programming Languages 1 - Lecture 5

    • Course: Programming Languages 1
    • Lecturer: Dr. Lina Murad
    • University: Al-Wataniya Private University
    • Course Focus: Introduces programming concepts and syntax in Java, including classes, inheritance, and polymorphism. Covers the fundamental concepts of object-oriented programming.

    Class Structure and Inheritance

    • Class Product: Stores product information: private String name;, private int price;. Includes constructor Product(String n, int p) for initialization and print() method to display product details. public double tax() returns a 2% tax calculation based on the price.
    • Class Toy: extends Product, adding an age attribute private int age. Includes constructor Toy(String n, int p, int a).
    • Example Errors: The notes highlight example code with errors for students to identify issues in class declarations and constructors.

    Polymorphism in Java

    • Polymorphism Overview: Polymorphism (meaning "many forms") allows a single method to behave differently depending on the object it's acting upon.
    • Compile-time Polymorphism: Achieved through method overloading. Methods with the same name but different parameters/signatures. The compiler figures out which method to call at compile time.
    • Runtime Polymorphism: Achieved through method overriding. Methods in child classes that have the same signature as a method in a parent class. The method called depends on the object type at runtime.
    • getClass() Method: Used to determine the exact class of an object at runtime.

    Inheritance Examples

    • Animal Class: Base class for animals, with the eat() method.
    • Dog Class: Inherits from Animal, overriding the eat() method for dogs.
    • BabyDog Class: Inherits from Dog, demonstrating inheritance and overriding.
    • Example Outputs: Showing the output of the code snippets. This illustrates how overriding works, and in some cases, how methods are called polymorphically based on the object referenced.

    Data Members and Upcasting

    • Data Members: Data members (attributes) in Java do not follow the rules of polymorphism. Their value is determined by the reference type, rather than the object's true type.
    • Upcasting: Concept where a reference variable of a parent class is used to refer to an object of a child class. During upcasting, the compiler decides which method will be called based on the type of reference variable used.

    Bank Example

    • Class Hierarchy: A hierarchical structure showing a Bank class with child classes (SBI, ICICI, AXIS).
    • getRateOfInterest(): Each child class implements getRateOfInterest() potentially returning different interest rates.

    Shape Example

    • Shape Class: A base class to represent various geometric shapes.
    • Rectangle and Circle Classes: Inherit from Shape, implementing specific geometric shapes with customized calculations and output.
    • Example Output: Sample output from the code to illustrate how the different shape types are categorized and processed.

    Abstract Class concept

    • Abstract Class: A class that cannot be instantiated. Classes with abstract class definitions are only usable as blueprints for subclasses.
    • abstract method: A method without an implementation, which ensures that child classes implement the method with their own particular implementations.

    Course Summary

    • The material demonstrates core concepts in Java object-oriented programming.
    • Practical examples and outputs are provided. The notes incorporate inheritance, polymorphism, and methods specific to the respective Java topics.

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    Description

    This quiz covers Lecture 5 of the Programming Languages 1 course, focusing on class structures, inheritance, and polymorphism in Java. Students will explore the implementation of classes, constructors, and error identification in object-oriented programming. Get ready to test your knowledge on the fundamental concepts presented by Dr. Lina Murad.

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