Introduction to Object-Oriented Programming
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Questions and Answers

What does CSS primarily define for HTML elements?

  • How elements are displayed on various media (correct)
  • The method of variable declaration
  • The data types used in JavaScript
  • The logical operations in code

Which of the following correctly describes the 'inline' method of adding CSS?

  • It defines styles for all pages within a website.
  • It applies styles to multiple web pages simultaneously.
  • It is used to style the entire document.
  • It uses the style attribute of an HTML element. (correct)

What is the purpose of JavaScript variables?

  • They store data values and are declared using the var keyword. (correct)
  • They are used to build the layout of web pages.
  • They store the presentation style of an HTML element.
  • They control the flow of CSS styles.

What does the '==' operator do in JavaScript?

<p>Tests for abstract equality with necessary type conversions. (A)</p> Signup and view all the answers

How can external CSS be linked to multiple HTML pages?

<p>By adding a link in the head section of the HTML document. (A)</p> Signup and view all the answers

Which statement about CSS selectors is true?

<p>They define patterns used to select HTML elements for styling. (A)</p> Signup and view all the answers

What is the role of the equal sign in JavaScript variables?

<p>It assigns values to variables. (A)</p> Signup and view all the answers

Which of the following is NOT a way to add CSS to HTML elements?

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

What is the purpose of method overriding in object-oriented programming?

<p>To provide a specific implementation of a method already defined in the parent class (D)</p> Signup and view all the answers

Which of the following correctly describes polymorphism?

<p>Ability for different classes to be treated as instances of the same class through a common interface (A)</p> Signup and view all the answers

Which of the following is NOT a type of constructor?

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

What is constructor overloading?

<p>Creating multiple constructors with different parameter lists (D)</p> Signup and view all the answers

Which keyword is used to indicate inheritance in Java?

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

What is the primary disadvantage of multiple inheritance in Java?

<p>It complicates the method resolution order and can lead to ambiguity (C)</p> Signup and view all the answers

What is one of the main advantages of inheritance?

<p>It allows methods to be overwritten for specific use cases (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of an object?

<p>Must have explicit return type (A)</p> Signup and view all the answers

In what scenario is a default constructor provided by the compiler?

<p>Only when no constructor is defined by the user (D)</p> Signup and view all the answers

What is the relationship represented by inheritance?

<p>IS-A relationship (C)</p> Signup and view all the answers

What is the minimum requirement to define a class in Java?

<p>Must have an access modifier (D)</p> Signup and view all the answers

Which type of inheritance implies a parent-child relationship where the child inherits from one parent?

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

Which statement is true regarding parameterized constructors?

<p>They provide different values to distinct objects (C)</p> Signup and view all the answers

What is polymorphism in object-oriented programming?

<p>The ability of an object to take on many forms (D)</p> Signup and view all the answers

Which of the following statements about method overriding is true?

<p>Method overriding occurs when a method in a subclass has the same name and parameters as a method in the superclass (B)</p> Signup and view all the answers

How does method overloading increase code reusability?

<p>By allowing methods with the same name to perform different tasks based on parameters (D)</p> Signup and view all the answers

What is the main advantage of using inheritance in programming?

<p>Facilitates code reusability and logical structure (D)</p> Signup and view all the answers

In Java, which type of constructors can a subclass use from its superclass?

<p>All types of constructors if properly invoked (C)</p> Signup and view all the answers

What is a key feature of abstract classes in Java?

<p>They can include both abstract and non-abstract methods. (C)</p> Signup and view all the answers

Which of the following describes the relationship between a parent class and a child class in a polymorphic scenario?

<p>A parent reference can hold a child class object and invoke its methods. (C)</p> Signup and view all the answers

How does encapsulation contribute to method overriding?

<p>It helps in hiding the internal workings of object methods. (B)</p> Signup and view all the answers

Which modifier allows a subclass to inherit a method without changing its behavior?

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

What is a characteristic of a constructor in Java?

<p>Constructors cannot have return types. (A)</p> Signup and view all the answers

What is the primary purpose of interfaces in Java?

<p>To describe a contract that implementing classes must follow (D)</p> Signup and view all the answers

Which of the following is a benefit of using interface over abstract class?

<p>A class can implement multiple interfaces, allowing flexibility. (A)</p> Signup and view all the answers

Which of the following is true regarding method visibility when using inheritance?

<p>Public methods of a superclass are accessible outside the package. (B)</p> Signup and view all the answers

What happens when you declare a method in a class as final?

<p>Its implementation cannot be changed in subclasses. (B)</p> Signup and view all the answers

Flashcards

Object (in OOP)

An entity with state (data) and behavior (methods). It's an instance of a class.

Class

A blueprint for creating objects. It defines the data (attributes) and actions (methods) for those objects.

Constructor (in OOP)

A special method used to initialize an object when it's created. It has the same name as the class.

Default Constructor

A constructor without any parameters. Automatically created if no other constructors are defined in a class.

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Parameterized Constructor

A constructor that takes parameters to initialize an object with specific values.

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Constructor Overloading

Having multiple constructors within a class with different parameter lists.

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Inheritance (OOP)

A mechanism where one class (subclass) acquires the properties and behaviors of another (superclass).

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Method Overriding(OOP)

A subclass provides a specific implementation of a method that is already defined by its super class.

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Single Inheritance

A subclass inherits from only one superclass.

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Runtime Polymorphism

The ability to call methods of different classes in the same way, selecting the appropriate method based on the object type.

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Data Hiding

Encapsulation of data inside a class to prevent direct access from outside the class.

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Code Reusability

Using existing code in different parts of a program or in other classes to avoid rewriting.

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Multilevel Inheritance

A subclass inherits from another subclass, which in turn inherits from a superclass.

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IS-A relationship

Describes inheritance, where a class is a specific type of another superclass.

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CSS Selectors

Patterns used to choose HTML elements for styling.

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JavaScript

Language that can change HTML and CSS, and manipulate data.

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JavaScript Variables

Store data values; declared with 'var'.

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Comparison Operator (==)

Tests for abstract equality, converting types when needed.

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Comparison Operator (===)

Tests for strict equality (no type conversion).

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Inline CSS

Applies a style to a single HTML element using the style attribute.

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External CSS

Defines styles for many HTML pages via a separate file linked in the head section.

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Polymorphism

The ability of an object to take on many forms, often when a parent reference is used to refer to a child class object.

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Method Overloading

A class having multiple methods with the same name but different parameters.

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Encapsulation

Wrapping code and data together into a single unit, giving control over data access.

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Abstract Class

A class that cannot be instantiated but can have abstract and non-abstract methods.

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Abstract method

A method that is declared abstract and does not have an implementation.

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Interface

A reference type similar to a class, containing abstract methods and used to achieve abstraction; a contract.

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Checked Exception

Exceptions that the compiler forces you to handle explicitly.

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Unchecked Exception

Exceptions that the compiler does not require explicit handling.

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Error

Problems that arise beyond the programmer's or user's control and typically ignored.

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Primary Key

A field in a table uniquely identifying each record.

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SQL

Structured Query Language, used to communicate with relational databases.

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Relational Database

A database that stores data in tables, allowing data to be related to each other.

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Collection Interface

Foundation of the Java Collections Framework, defining core methods for all collections.

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Array

An object storing elements of the same data type, fixed in size.

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Queue

A collection following FIFO (First-In, First-Out) order.

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ArrayList

A dynamic array implementation of the List interface.

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Study Notes

Object

  • An entity that has state and behavior
  • Can be defined as an instance of a class
  • Contains an address
  • Takes up space in memory
  • Can communicate without knowing details of other objects' data or code. Only needs to know the type of message accepted and response type by the objects.
  • Must have no explicit return type
  • Cannot be abstract, static, final, and synchronized

Class

  • Templates used to create objects and define object data types and methods
  • Core properties: data types and methods
  • Can be defined as a blueprint
  • Don't consume space
  • A blueprint for creating individual objects

Advantages of OOPs over Procedure Oriented Programming

  • Easier development and maintenance
  • Procedure oriented programming is harder to manage if code grows
  • Provides data hiding
  • Procedure oriented programming language has global data that can be accessed anywhere.

Constructor

  • Block of code similar to a method
  • Called when an object instance is created
  • Allocates memory for the object
  • Used to initialize the object
  • Called when an object is created
  • Like a method but without a return type
  • Rules: Method name must be the same as class name

Parameterized Constructor

  • Has a specific number of parameters
  • Used to provide different values to different objects

Constructor Overloading

  • Technique of having one or more constructors with different parameter lists
  • Each constructor performs a different task
  • Distinguished by the number and types of parameters

Inheritance

  • A mechanism where one object acquires all properties and behaviors of a parent object
  • An important part of OOPs
  • Can reuse methods and fields of the parent class
  • Can add new methods and fields in the current class
  • Represents an "is-a" relationship

Advantages of Inheritance

  • Method overriding
  • Code reusability

Multiple Inheritance

  • Not supported by Java
  • Reduces complexity and simplifies language
  • Improves the language

Polymorphism

  • The ability of an object to take many forms
  • Parent class references can be used to refer to a child class object

Method Overloading

  • A class can have multiple methods with the same name but different parameters
  • Improves readability of the program
  • Parameters must be different
  • Compile-time Polymorphism

Static Method Overriding

  • Not possible
  • Static methods are bound to the class, not the object

Abstraction

  • Hiding implementation details and showing only functionality to the user
  • Focusing on what an object does, not how it does it
  • Achieved through abstract classes or interfaces

Generalization

  • Extracting shared characteristics from two or more classes and combining into a generalized superclass

Specialization

  • Creating new subclasses from an existing class

Abstract Class

  • Declared abstract
  • Can have abstract and non-abstract methods
  • Needs to be extended

Package

  • Group of similar classes, interfaces, and subpackages
  • Built-in vs user-defined packages
  • Organizes code and makes it easier to maintain

Interface

  • Similar to a class but only has abstract methods
  • Methods are implicitly abstract and public
  • Can implement multiple interfaces
  • Cannot contain instance variables (only static or final)
  • Cannot instantiate like a class

Class and Interface Similarities

  • Can have multiple methods
  • Name of the interface matches the file name
  • Byte code of the interface appears in a .class file

Differences Between Classes and Interfaces

  • Interfaces cannot be instantiated
  • Interfaces cannot have constructors
  • Methods in interfaces are abstract
  • Interfaces cannot have instance fields (only static or final)

Exception Handling

  • Checked Exceptions: Compiler forces you to handle them explicitly in methods. Methods throwing checked exceptions must include a throws clause
  • Unchecked Exceptions (Errors): Compiler does not enforce handling. Methods don't need a throws clause. Errors typically indicate an exceptional condition not recoverable
  • Exception Hierarchy: An hierarchy of exception classes, extending from Throwable class. Exception is a subclass of Throwable.

Catching Exceptions

  • Method catches exception using try and catch keywords
  • Code prone to exceptions is placed in the try block
  • Exception handled by corresponding catch block

Throw and Throws

  • throws is used to declare (or specify), that a method may throw an exception
  • throw is used to explicitly generate an exception

Finally Block

  • Always executes, regardless of exception
  • Used for cleanup actions (resource release).

Arrays

  • An object that contains elements of a similar data type.
  • Elements are stored at indices (starting from 0).

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Description

This quiz covers the fundamental concepts of Object-Oriented Programming (OOP), including the definitions of objects and classes, their properties, and advantages over procedure-oriented programming. Additionally, it addresses the role of constructors in object creation. Test your understanding of these essential programming principles.

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