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What is the term used to describe the process of hiding specific details of an object and revealing only essential information?
What is the term used to describe the process of hiding specific details of an object and revealing only essential information?
Data abstraction
What are the two main ways to achieve data abstraction?
What are the two main ways to achieve data abstraction?
The 'abstract' keyword is an access modifier in Java.
The 'abstract' keyword is an access modifier in Java.
False
What is a characteristic of an abstract class?
What is a characteristic of an abstract class?
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What is the purpose of an abstract method?
What is the purpose of an abstract method?
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An abstract class can have both abstract and regular (non-abstract) methods.
An abstract class can have both abstract and regular (non-abstract) methods.
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An abstract method can be implemented within a non-abstract class.
An abstract method can be implemented within a non-abstract class.
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When a subclass inherits an abstract class but does not implement all of its abstract methods, the subclass must be:
When a subclass inherits an abstract class but does not implement all of its abstract methods, the subclass must be:
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Which of these best describes the purpose of the 'abstract' keyword in method declaration?
Which of these best describes the purpose of the 'abstract' keyword in method declaration?
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What is the meaning of the statement 'A subclass can be abstract even if its superclass is concrete'?
What is the meaning of the statement 'A subclass can be abstract even if its superclass is concrete'?
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A concrete class can contain an abstract method.
A concrete class can contain an abstract method.
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When is abstraction usually used?
When is abstraction usually used?
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Abstraction is a simple concept that focuses on hiding data using getters and setters.
Abstraction is a simple concept that focuses on hiding data using getters and setters.
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Abstraction is the process of hiding certain details and showing only essential information to the user. This can be achieved with either abstract classes or interfaces.
Abstraction is the process of hiding certain details and showing only essential information to the user. This can be achieved with either abstract classes or interfaces.
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The 'abstract' keyword is a non-access modifier, used for classes and methods.
The 'abstract' keyword is a non-access modifier, used for classes and methods.
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'Abstract class: is a restricted class that cannot be used to create objects (to access it, it must be inherited from another class).'
'Abstract class: is a restricted class that cannot be used to create objects (to access it, it must be inherited from another class).'
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'Abstract method: can only be used in an abstract class, and it does not have a body. The body is provided by the subclass (inherited from).'
'Abstract method: can only be used in an abstract class, and it does not have a body. The body is provided by the subclass (inherited from).'
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'**An abstract class can have both abstract and regular methods':'
'**An abstract class can have both abstract and regular methods':'
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Class abstraction means to separate class implementation from the use of the class. The creator of the class provides a description of the class and lets the user know how the class can be used. The detail of implementation is encapsulated and hidden from the user.
Class abstraction means to separate class implementation from the use of the class. The creator of the class provides a description of the class and lets the user know how the class can be used. The detail of implementation is encapsulated and hidden from the user.
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Study Notes
Object-Oriented Programming Concepts - Abstraction
- Abstraction is the process of hiding certain details and showing only essential information to the user.
- It focuses on what an object does, not how it does it.
- Abstraction can be achieved using abstract classes or interfaces.
- The
abstractkeyword is a non-access modifier used for classes and methods.
Abstract Classes
- A class declared as
abstractcannot be instantiated. - To utilize an abstract class, it must be inherited from another class.
- Abstract classes can contain both abstract and regular methods.
- If a class has at least one abstract method, it must be declared
abstract. - Abstract methods lack a method body.
- Subclasses (inherited classes) must implement abstract methods.
Abstract Methods
- Method declared as
abstracthas no body (no implementation). - The abstract keyword precedes the abstract method declaration.
- An abstract method only contains a method signature and a semicolon (;), not curly braces {}.
Abstract Class vs. Concrete Class
- Abstract classes cannot be instantiated with
new. - Concrete classes can be instantiated with
new.
Example of an abstract class
abstract class Bike {
abstract void run();
void changeGear() {
System.out.println("Gear changed");
}
}
-
run()is an abstract method, it has no implementation. -
changeGear()is a concrete method, it has an implementation (method body). - Concrete subclass Honda extends this abstract class and provides an implementation for the
run()method.
When to Use Abstract Classes and Methods
- Abstract methods and classes are useful when multiple subclasses need to implement similar but different behaviors.
- This creates a common interface for the subclasses.
Declaring a Method as Abstract
- The class containing the abstract method must be declared abstract.
- Any inheriting class must either override the abstract method or declare itself as abstract.
Output examples demonstrating the functionality of abstract classes and methods.
- Various program examples demonstrating object instantiation, method invocation, and output details from abstract class/methods.
Differences between Abstraction and Encapsulation
- Abstraction hides implementation details, emphasizing what an object does.
- Encapsulation bundles data and methods together, concealing data from outside access.
- Abstraction is a design-level concept.
- Encapsulation is an implementation-level technique.
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Description
This quiz covers the fundamental concepts of abstraction in Object-Oriented Programming. Learn how abstraction is used to hide unnecessary details and focus on what an object does. Understand the roles of abstract classes and methods, along with their implementations.
