Object-Oriented Programming in Java (BCA30108)
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Questions and Answers

What is the role of class D in the provided code?

  • It serves as a superclass for the other classes.
  • It implements multiple interfaces and extends a class. (correct)
  • It represents a simple data holder without functionality.
  • It is an abstract class with unimplemented methods.

What will be the output when the main method of HybridExample is executed?

  • Class C Class C Class C
  • Interface A Interface B Class C (correct)
  • Class C Interface A Interface B
  • Interface B Class C Interface A

In the context of inheritance, what defines a subclass?

  • A class that encapsulates multiple classes within itself.
  • A class that can only inherit from one superclass.
  • A class that does not inherit any properties.
  • A class that inherits properties and behaviors from a superclass. (correct)

Which of the following best describes hybrid inheritance?

<p>A combination of various inheritance types within a single class. (D)</p> Signup and view all the answers

What is the function 'displayC' of class C expected to return?

<p>It returns the string 'Class C'. (C)</p> Signup and view all the answers

What type of inheritance is demonstrated by the relationship between the classes Dog and Mammal?

<p>Multilevel Inheritance (B)</p> Signup and view all the answers

In the context of object-oriented programming, which class will be able to invoke the method 'eat'?

<p>Both Dog and Cat (C)</p> Signup and view all the answers

What will be the output of the following code when executing the Main class?

<p>This animal eats food. The dog barks. The cat meows. (B)</p> Signup and view all the answers

Which type of inheritance allows multiple subclasses to inherit from a single superclass?

<p>Hierarchical Inheritance (D)</p> Signup and view all the answers

Which of the following statements is true about interfaces in Java?

<p>They can achieve multiple inheritance in a class. (D)</p> Signup and view all the answers

In which situation would you use multilevel inheritance?

<p>When a subclass needs to extend another subclass. (D)</p> Signup and view all the answers

What keyword is used in Java to denote a class that inherits from another class?

<p>extends (A)</p> Signup and view all the answers

Which method would you expect the instance of the Dog class to execute in the given Main class?

<p>bark (B)</p> Signup and view all the answers

What is the primary benefit of using inheritance in object-oriented programming?

<p>It allows code reusability and hierarchical class structure. (C)</p> Signup and view all the answers

Which statement describes single inheritance?

<p>A subclass inherits from only one superclass. (C)</p> Signup and view all the answers

In the code provided, what is the output when the Child object's display method is called?

<p>This is the parent class. (A)</p> Signup and view all the answers

Which keyword is used to specify that a class is inheriting from another class?

<p>extends (C)</p> Signup and view all the answers

What would happen if a subclass did not override a method from its superclass?

<p>The subclass inherits the method from the superclass without changes. (B)</p> Signup and view all the answers

What is the purpose of the 'super' keyword in Java?

<p>To call a method from the superclass. (B)</p> Signup and view all the answers

In the provided example, which class is considered the superclass?

<p>Parent (A)</p> Signup and view all the answers

How does inheritance relate to the concept of dynamic method dispatch?

<p>It enables the correct method call based on object type at runtime. (D)</p> Signup and view all the answers

What is the purpose of the super keyword in a subclass?

<p>To call a superclass constructor or access its members (B)</p> Signup and view all the answers

How can a class be made non-inheritable in Java?

<p>By declaring it as a <code>final</code> class (B)</p> Signup and view all the answers

What does the final keyword do when applied to a method?

<p>It prevents the method from being overridden in subclasses (A)</p> Signup and view all the answers

What is the main feature of dynamic method dispatch?

<p>It resolves method calls at runtime based on the object's actual type (C)</p> Signup and view all the answers

When is a variable declared with the final keyword in Java reassigned?

<p>It can never be reassigned once initialized (A)</p> Signup and view all the answers

What is the accessibility level of the 'brand' and 'model' variables in the Vehicle class?

<p>Protected (A)</p> Signup and view all the answers

Which class represents a superclass in the vehicle hierarchy example?

<p>Vehicle (D)</p> Signup and view all the answers

What type of methods are start() and stop() in the Vehicle class?

<p>Abstract methods (C)</p> Signup and view all the answers

Why should inheritance be used judiciously as mentioned in the content?

<p>To avoid tight coupling between classes (D)</p> Signup and view all the answers

Which subclass provides an implementation for the start() method?

<p>Car (B), Motorcycle (C)</p> Signup and view all the answers

What does the term 'loose coupling' refer to in regards to software design?

<p>Classes that do not affect each other's behavior (B)</p> Signup and view all the answers

What package accessibility level allows classes inside the same package to access the members?

<p>Default (A)</p> Signup and view all the answers

Which design principle can improve code organization and maintainability?

<p>Well-designed packages (A)</p> Signup and view all the answers

What will be the output of the main method in DynamicDispatchExample?

<p>Child1 class method followed by Child2 class method (D)</p> Signup and view all the answers

Which of the following statements about abstract classes is true?

<p>An abstract class can have concrete methods. (B)</p> Signup and view all the answers

What does the interface Drawable require its implementing classes to do?

<p>Provide an implementation for the draw() method. (D)</p> Signup and view all the answers

What is the correct way to create a package named mypackage in Java?

<p>package mypackage; (B)</p> Signup and view all the answers

What is the accessibility of public members in Java packages?

<p>Accessible from any class in any package. (D)</p> Signup and view all the answers

In the context of object-oriented programming, what is dynamic dispatch?

<p>The choice of method implementation at runtime based on the object's actual type. (A)</p> Signup and view all the answers

Which of the following statements is incorrect regarding subclasses of an abstract class?

<p>Subclasses can call the abstract class methods without implementation. (A)</p> Signup and view all the answers

What will happen if a class does not implement all methods defined in an interface it declares to implement?

<p>The class will need to be declared abstract. (D)</p> Signup and view all the answers

Flashcards

What is Inheritance?

A fundamental OOP concept where new classes (subclasses) inherit properties and behaviors from existing classes (superclasses). This promotes code reuse and creates a hierarchical class structure.

Single Inheritance

A subclass inherits properties and behaviors from only one superclass. Like a child inheriting from one parent.

Multiple Inheritance

A subclass inherits from multiple superclasses. Like a child inheriting from both parents.

Multilevel Inheritance

A hierarchy where a superclass inherits from another superclass, which might inherit from another. Like a family tree with grandparents, parents, and children.

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The 'super' Keyword

The keyword 'super' refers to the superclass. Use it to access superclass methods or constructors within subclasses.

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The 'final' Keyword

The keyword 'final' prevents subclasses from overriding methods marked as 'final' in the superclass. They remain fixed and unchangeable.

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Dynamic Method Dispatch

The process where the actual method execution depends on the object's type at runtime, not compile time. This allows polymorphism and flexibility.

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Abstract Classes

Abstract classes cannot be instantiated directly. They act as blueprints for subclasses, often containing abstract methods that must be implemented in subclasses.

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Hierarchical Inheritance

Multiple subclasses inherit from a single superclass.

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Inheritance

In object-oriented programming, a subclass inherits properties and methods from a superclass.

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Superclass

The class that provides properties and methods to be inherited.

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Subclass

The class that inherits properties and methods from a superclass.

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Method Overriding

A mechanism that allows a subclass to override methods from its superclass.

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Hybrid Inheritance

A type of inheritance where a subclass inherits properties and behaviors from multiple superclasses, like a child inheriting traits from both parents.

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Hybrid Class

A class that inherits from a superclass and also implements one or more interfaces.

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Interface

A class that defines a set of methods that must be implemented by any class that inherits from it.

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What is the purpose of the 'super' keyword?

The super keyword is used within a subclass to access methods, constructors, or variables of its immediate superclass.

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How does the 'final' keyword affect a class?

Declaring a class as final prevents it from being extended (meaning no subclasses can inherit from it).

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What is the effect of declaring a method as 'final'?

When a method is declared as final, it cannot be overridden by subclasses. The method's implementation remains fixed.

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What is the effect of declaring a variable as 'final'?

The final keyword can also be applied to variables. A final variable cannot be reassigned after its initial value is set.

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What is Dynamic Method Dispatch?

Dynamic method dispatch allows you to call a method on an object, and the specific method executed depends on the object's actual type at runtime. This enables polymorphism. For example, a method call on a Dog object might behave differently than the same call on a Cat object, even though both might inherit the method from the same Animal class.

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Abstract Method

A method declared without a body in an abstract class. Subclasses must provide implementation details.

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Dynamic Dispatch

The mechanism where the actual call to a method is decided at runtime, based on the object's actual type.

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Package

A namespace that organizes a set of related classes and interfaces.

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Import Statement

Used to import classes or interfaces from other packages.

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Member Access

A way to access members (methods, variables) of a class, based on their visibility.

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Public

A visibility modifier meaning the member can be accessed from any class in any package.

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What is an abstract class?

A class that cannot be directly instantiated. Serves as a blueprint for subclasses. Often contains abstract methods that must be implemented by subclasses.

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What happens when a subclass implements an interface?

When a subclass implements an interface, it inherits all its methods and must provide its own implementation.

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What is a subclass?

A subclass is more specialized, inheriting attributes and behaviors from a superclass.

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What is an interface?

A class that defines a set of methods that must be implemented by any class that inherits from it.

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What is a superclass?

The class that provides properties and methods to be inherited by subclasses. It acts as a blueprint for its descendants.

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What is method overriding?

Allows a subclass to override methods from its superclass. It allows subclasses to provide their own implementation for inherited methods.

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Study Notes

Object-Oriented Programming in Java (BCA30108)

  • Inheritance: A fundamental OOP concept enabling creation of new classes (subclasses) inheriting properties and behaviors from existing classes (superclasses). This promotes code reusability and hierarchical structure.

Types of Inheritance

  • Single Inheritance: A subclass inherits from only one superclass.

    • Diagram illustrating the relationship between base class and derived class.
    • Example code demonstrating single inheritance. Output showcasing both parent and child class methods being called.

  • Multiple Inheritance: A subclass inherits from multiple superclasses.

  • Multilevel Inheritance: A subclass inherits from a subclass, creating a chain of inheritance.

    • Diagram illustrating this.
    • Example code exemplifying this, with output showing chain of inheritance.

  • Hierarchical Inheritance: Multiple subclasses inherit from a single superclass (base class). - Diagram illustrating this.

    • Example code for hierarchical inheritance. Output illustrating call to parent methods by subclass.

  • Hybrid Inheritance: A combination of multiple inheritance types.

    • Diagram illustrating this form of inheritance.

Use of Keywords: super and final

  • super Keyword:

    • Used to access members (variables and methods) of a superclass from a subclass.
    • Used to call constructors of a superclass.
    • Code examples showing usage of super for method calls and constructor calls within a subclass.

  • final Keyword:

    • To prevent a class from being inherited.
    • Used to prevent a method from being overridden in a subclass.
    • Used to prevent a variable from being reassigned after initialization.
    • Code examples.

Dynamic Method Dispatch (Polymorphism)

  • Dynamic method dispatch allows methods to be called on objects based on their actual type at runtime, not compile time.
  • This achieves polymorphism.
  • Example demonstrating how calling the method on different subclasses returns different outputs.
  • Code illustration.

Abstract Classes and Methods

  • Abstract class cannot be instantiated directly (can't create objects from it).
  • Abstract methods do not have implementation but provide a signature for subclasses to implement.
  • Abstract classes can be used to enforce a common interface.
  • Code examples.

Interfaces

  • An interface defines a set of methods that a class must implement.
  • Interfaces define a blueprint for classes.
  • Classes can implement multiple interfaces.
  • Code examples.

Packages

  • Packages are namespaces that organize classes and interfaces logically.
  • Creating packages, importing packages, member access control mechanisms are demonstrated by code.

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Object Oriented Programming in JAVA (BCA30108) Module-3 Notes PDF

Description

Explore the concept of Inheritance in Object-Oriented Programming through Java. This quiz covers various types of inheritance including single, multiple, multilevel, and hierarchical inheritance. Test your understanding with examples and diagrams that illustrate these key OOP principles.

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