Inheritance in Programming Languages
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Questions and Answers

What is inheritance in Java?

Inheritance in Java is creating new classes based on existing classes.

What is the advantage of using inheritance?

Inheritance allows for code reuse and creates a relationship between classes that emphasizes the "is-a" relationship.

What is the relationship between the superclass and subclass in inheritance?

The superclass is the parent class and the subclass is the child class. The subclass inherits properties and methods from the superclass.

In the example provided, which class is the superclass and which is the subclass?

<p>The superclass is Employee and the subclass is Programmer.</p> Signup and view all the answers

What are the three types of inheritance?

<p>Multilevel (A), Hierarchical (C), Single (D)</p> Signup and view all the answers

What is the difference between single and multilevel inheritance?

<p>Single inheritance involves one subclass inheriting from one superclass. Multilevel inheritance involves multiple levels of inheritance, where a subclass inherits from a superclass, which itself inherits from another superclass.</p> Signup and view all the answers

What is hierarchical inheritance?

<p>Hierarchical inheritance involves multiple subclasses inheriting from a single superclass.</p> Signup and view all the answers

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

<p>The 'extends' keyword is used to indicate that a class is inheriting from another class. This creates a superclass-subclass relationship.</p> Signup and view all the answers

What is overriding in Java?

<p>Overriding occurs when a subclass provides its own implementation for a method that already exists in its superclass. This allows the subclass to change how that method behaves.</p> Signup and view all the answers

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

<p>The 'super' keyword allows a subclass to refer to members of its superclass, specifically to access overridden methods or to call superclass constructors.</p> Signup and view all the answers

Flashcards

Inheritance in Java

In Java, inheritance allows creating new classes based on existing ones. It promotes code reusability and enhances code organization.

Inheritance: Access to Parent Class Fields and Methods

When a class inherits from another class, it gains access to the parent class's fields and methods. These can be used and modified by the child class.

IS-A Relationship

A type of relationship in object-oriented programming where one class (the child class) is a specific type of another class (the parent class).

Super Class

The existing class being inherited from. It forms the basis for the new class.

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Sub Class

The new class created through inheritance. It inherits from the super class and can add its own features.

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Employee and Programmer Example

An example of inheritance: The 'Employee' class represents the general concept of an employee, while the 'Programmer' class represents a specific type of employee (a programmer).

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Programmer IS-A Employee

This statement expresses the IS-A relationship: A 'Programmer' is a type of 'Employee'.

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A Programmer is a Employee

This statement uses the words 'a' and 'is a' to indicate inheritance. This helps to visualize the IS-A relationship

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Protected Variables in Inheritance

In Java, a protected variable defined within a super class can be accessed by the child class as if it were 'public'.

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Overriding

The process of redefining a method in a child class that already exists in the parent class. This allows for specialized behavior in the child class.

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Overriding Method Signature

When overriding a method, the child class method has the same name and parameters as the parent class method, but with a different implementation to create specific behavior.

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Overriding: Explicit Definition

A method in a parent class can be overridden in a child class by using the 'override' keyword. This is a way to explicitly define a custom behavior for that method.

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Creating an Employee Object Array

To create a new object of the 'Employee' class, an array can be declared that holds 'Employee' objects. This can be used to store and manage multiple employee records.

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Study Notes

Inheritance in Programming Languages

  • Inheritance allows creating new classes based on existing ones.
  • When inheriting from an existing class, you reuse its fields and methods.
  • You can add new methods and fields to the new class.
  • Inheritance represents an IS-A relationship (also called a parent-child relationship).
  • The existing class is the superclass, and the new class is the subclass.

Types of Inheritance

  • Single: A subclass inherits from only one superclass.
  • Multilevel: A subclass inherits from a superclass that, in turn, inherits from another superclass.
  • Hierarchical: Multiple subclasses inherit from a single superclass.

Example: Programmer and Employee

  • Employee is the superclass (parent class).
  • Programmer is the subclass (child class).
  • The Programmer class (subclass) inherits attributes and methods from the Employee class (superclass) that are relevant. It can add additional data to describe programmer roles.

Code Example (Java)

  • Person Class: Defines basic attributes like ID and name.
  • Employee Class: Inherits from Person and adds a salary field.
  • Methods to handle printing information and adding to salary are included.

Overriding in Inheritance

  • If a superclass has a method, a subclass can create a method with the same name and parameters.
  • This action is called overriding.
  • The subclass method replaces the superclass method. This lets the subclass customize the behavior implemented by the superclass's method.

Example Usage

  • Create objects using the defined classes.
  • Use the methods to manipulate the data.
  • Use inheritance to create methods for a specific class from existing method in superclass.

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Description

This quiz explores the concept of inheritance in programming languages, focusing on how new classes can be created based on existing ones. It covers various types of inheritance, including single, multilevel, and hierarchical inheritance, with practical examples to illustrate the IS-A relationship between classes.

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