Java Inheritance Overview
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which method is used to check if a file exists in Java?

  • fileExists()
  • isFile()
  • exists() (correct)
  • isExist()

Which class is utilized for file creation in Java?

  • File (correct)
  • FileInputStream
  • FileReader
  • FileWriter

What is the correct method to create a new file in Java?

  • makeFile()
  • createNewFile() (correct)
  • createFile()
  • newFile()

Which method can be used to delete a file in Java?

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

What exception occurs when attempting to read a non-existent file in Java?

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

What is the main purpose of inheritance in Java?

<p>To enable code reuse (C)</p> Signup and view all the answers

Which keyword is specifically used for creating a subclass in Java?

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

Which of the following describes what a subclass can inherit from a superclass in Java?

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

Which of the following statements regarding the inheritance model in Java is true?

<p>A class can inherit only one parent class (D)</p> Signup and view all the answers

What is the correct method of invoking a superclass constructor within a subclass in Java?

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

Regarding method overriding in Java, what is accurately described?

<p>A subclass can change the implementation of a superclass method (A)</p> Signup and view all the answers

What can be inherited by subclasses in Java?

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

Can a subclass in Java override a private method present in its superclass?

<p>No, private methods cannot be accessed (C)</p> Signup and view all the answers

What will be the output of the following code snippet?

class Parent {
    void display() {
        System.out.println("Parent class");
    }
}

class Child extends Parent {
    void display() {
        System.out.println("Child class");
    }
}

public class Main {
    public static void main(String[] args) {
        Parent obj = new Child();
        obj.display();
    }
}

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

What happens if a subclass does not provide a constructor?

<p>A default constructor is provided by the compiler (C)</p> Signup and view all the answers

Can a subclass call a private method of its superclass?

<p>No, private methods are not inherited (A)</p> Signup and view all the answers

What is the superclass of all classes in Java?

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

Which of the following allows for runtime polymorphism in Java?

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

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

<p>To provide a specific implementation for a method defined in the superclass (B)</p> Signup and view all the answers

Which access modifiers can be used for a method in a superclass so that it can be overridden by a subclass?

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

What does the keyword 'final' signify in relation to methods in Java?

<p>The method cannot be modified or overridden (A)</p> Signup and view all the answers

What will happen if you override a method with a different return type?

<p>It is allowed if the return type is a subclass of the original return type (C)</p> Signup and view all the answers

What is true about the constructors in abstract classes?

<p>Abstract classes can have constructors but cannot instantiate objects (B)</p> Signup and view all the answers

Can we override the constructor in Java?

<p>No (B)</p> Signup and view all the answers

What does the super keyword refer to?

<p>The superclass of the current class (B)</p> Signup and view all the answers

What is the result of trying to call an instance method on a null reference in Java?

<p>A NullPointerException will be thrown at runtime (C)</p> Signup and view all the answers

What can be inferred about Vehicle v = new Car(); v.run(); in the given code snippet?

<p>The code is valid and will display 'Car is running' (C)</p> Signup and view all the answers

Can a subclass access the private variables of its superclass in Java?

<p>Yes, through getter and setter methods (A)</p> Signup and view all the answers

What happens if a subclass does not override an abstract method?

<p>The subclass will fail to compile (B)</p> Signup and view all the answers

Which of the following can be inherited by a subclass?

<p>All of the above (D)</p> Signup and view all the answers

Can an abstract class implement an interface?

<p>Yes, it can leave some methods unimplemented (D)</p> Signup and view all the answers

What is the keyword used to declare an interface in Java?

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

In Java, what does the term 'multiple inheritance' refer to?

<p>A class inheriting from multiple classes (D)</p> Signup and view all the answers

Can a class implement multiple interfaces in Java?

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

What is a subclass in Java?

<p>A class that inherits from a superclass (B)</p> Signup and view all the answers

What is a key characteristic of a final class in Java?

<p>It cannot be subclassed (A)</p> Signup and view all the answers

What exception type does Java throw when trying to read from a non-existent file?

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

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

<p>All methods in an interface are public by default (B)</p> Signup and view all the answers

What can a subclass not do regarding protected members inherited from the superclass?

<p>Access them from a static context (C)</p> Signup and view all the answers

What keyword is used to denote a method that cannot be implemented in the current class?

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

Flashcards

Java Inheritance

A mechanism in Java for creating a new class from an existing one, inheriting its properties and methods.

Inheritance Keyword

The keyword 'extends' is used to inherit from a class in Java.

Purpose of Inheritance

The primary purpose is code reuse and creating an efficient structure by deriving from an existing class.

Inheritance Syntax

The correct syntax is 'class Child extends Parent;

Signup and view all the flashcards

Inherited Components

A subclass inherits both methods and variables from a superclass.

Signup and view all the flashcards

Multiple Inheritance

In Java, a class can inherit from only one parent class. (Not multiple classes).

Signup and view all the flashcards

Superclass of Object Class

The Object class has no direct superclass; it's at the top of the inheritance hierarchy.

Signup and view all the flashcards

Inheritable Components (Methods and Variables)

Subclasses can inherit methods and variables defined in their superclasses.

Signup and view all the flashcards

Method Overriding restrictions

Subclasses can't override private methods inherited from superclasses.

Signup and view all the flashcards

Method Overriding

A subclass provides its own implementation of a method from its superclass.

Signup and view all the flashcards

Calling Superclass Constructor

The 'super()' keyword in the subclass constructor calls the superclass's constructor.

Signup and view all the flashcards

Checking if a file exists in Java

The exists() method is used to determine if a file or directory specified by a given path exists.

Signup and view all the flashcards

Getting a file's size in Java

The length() method of the File class returns the size of a file in bytes.

Signup and view all the flashcards

Creating a file in Java

Use the File class to create a file.

Signup and view all the flashcards

Creating a new file in Java

Use the createNewFile() method of the File class to create a new, empty file.

Signup and view all the flashcards

Deleting a file in Java

The delete() method of the File class is used to delete a file.

Signup and view all the flashcards

Subclass in Java

A class that inherits properties and behaviors from another class (the superclass).

Signup and view all the flashcards

Superclass in Java

A class from which another class (subclass) inherits properties and behaviors.

Signup and view all the flashcards

Runtime Polymorphism

The ability for a method call to choose the appropriate implementation based on the object type at runtime.

Signup and view all the flashcards

Inheritance in Java

The process where a subclass acquires the properties and behaviors of a superclass.

Signup and view all the flashcards

super keyword

Used to refer to the superclass's members (methods and variables).

Signup and view all the flashcards

Constructors in Java

Special methods used to initialize objects of a class.

Signup and view all the flashcards

Private Method Inheritance

A subclass cannot directly inherit or call a private method from its superclass.

Signup and view all the flashcards

Final Method

A method that cannot be overridden by subclasses.

Signup and view all the flashcards

Object Class

The ultimate parent class of all objects in Java.

Signup and view all the flashcards

Static Method Inheritance

Subclasses inherit static methods, but the object from the subclass will call the superclass method.

Signup and view all the flashcards

Access Modifiers

Keywords used to control the visibility (accessibility) of class members.

Signup and view all the flashcards

Interface in Java

A blueprint for a class with only abstract methods and constants.

Signup and view all the flashcards

Method overriding in Java

A subclass provides a specific implementation of a method that is already present in its superclass, allowing the behavior of the method to change depending on the object type.

Signup and view all the flashcards

super() constructor

A keyword used in a subclass constructor to explicitly call the constructor of the superclass, initializing the instance variables of the superclass.

Signup and view all the flashcards

Abstract class in Java

A class that cannot be instantiated directly but can be inherited. Primarily serves as a blueprint for other classes, defining common methods.

Signup and view all the flashcards

Final class in Java

A class that cannot be extended (inherited from).

Signup and view all the flashcards

Multiple inheritance through classes

A concept where a class can inherit from multiple parent classes. Not supported directly in Java.

Signup and view all the flashcards

Implementing interface methods

Subclasses must provide an implementation for all methods declared in the interface they implement.

Signup and view all the flashcards

Abstract method in Java

A method declared without an implementation in an abstract class.

Signup and view all the flashcards

final method in Java

A method that cannot be overridden by subclasses.

Signup and view all the flashcards

createNewFile() method

Creates a new file in Java. If no errors occur, a new file is created. It returns a Boolean value (true or false) to indicate if the file was created.

Signup and view all the flashcards

delete() method

Deletes a file in Java.

Signup and view all the flashcards

FileNotFoundException

Exception in Java thrown when a file doesn't exist at the specified path when trying to read it.

Signup and view all the flashcards

Calling a superclass method

In a subclass, using super.methodName() to invoke the superclass's version of a method.

Signup and view all the flashcards

NullPointerException

Exception in Java thrown when trying to access a member of an object reference that is null.

Signup and view all the flashcards

Study Notes

Java Inheritance

  • Inheritance: A mechanism for creating new classes (subclasses) based on existing classes (superclasses), enabling code reuse.
  • Keyword for Inheritance: extends
  • Purpose of Inheritance: Primarily for code reuse, enabling subclasses to inherit methods and variables from superclasses.
  • Syntax for Inheritance: class Subclass extends Superclass
  • Inherited Members: Subclasses inherit both methods and variables from their superclasses.
  • Single Inheritance (Java): A class can inherit from only one superclass.
  • Superclass of all classes: The Object class.
  • Method Overriding: A subclass providing its own implementation of a method already present in its superclass.
  • Calling Superclass Constructor: super() is used in a subclass's constructor to invoke the superclass's constructor.
  • Default Constructor: If a subclass doesn't define a constructor, the compiler provides a default one.
  • Private Methods: Subclasses cannot override private methods of their superclasses.
  • Runtime Polymorphism: Achieved using method overriding and method overloading, allowing different implementations based on object types.
  • Superclass: The class from which other classes inherit, providing shared methods and variables.
  • Access Modifiers and Overriding: private, protected, and public methods in the superclass can be overridden in subclasses. A final method in the superclass cannot be overridden.
  • Multiple Inheritance (Restriction): Java does not allow multiple inheritance through classes but allows it through interfaces.
  • Abstract Methods: Methods with no implementation; declared in abstract classes. A subclass is required to provide an implementation for them.

Java File Handling

  • File Class: Used to create and manipulate files.
  • Creating a file: Use the createNewFile() method of the File class.
  • Deleting a file: Use the delete() method of the File class.
  • Checking if file exists: The exists() method of the File class.
  • File size: Use the length() method (File) to obtain the size of a file.
  • FileNotFoundException: Thrown if a file doesn't exist during read operations.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Description

This quiz covers the fundamental concepts of inheritance in Java, including the definition, purpose, and syntax. Learn how subclasses inherit characteristics from superclasses and the importance of method overriding. Test your understanding of key terms and principles related to Java inheritance.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser