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Questions and Answers
A class is an instance of an object in Java.
A class is an instance of an object in Java.
False
Inheritance is the process of creating a new object based on an existing object.
Inheritance is the process of creating a new object based on an existing object.
False
Polymorphism can be achieved through method overriding and method overloading.
Polymorphism can be achieved through method overriding and method overloading.
True
Encapsulation is the concept of dividing data and methods into separate units.
Encapsulation is the concept of dividing data and methods into separate units.
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Abstraction is achieved through concrete classes and interfaces in Java.
Abstraction is achieved through concrete classes and interfaces in Java.
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Composition is the concept of creating objects from scratch.
Composition is the concept of creating objects from scratch.
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Public access modifier means that the class or method can be accessed only within the same class.
Public access modifier means that the class or method can be accessed only within the same class.
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A subclass can inherit the properties and behaviors of multiple superclasses.
A subclass can inherit the properties and behaviors of multiple superclasses.
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Method overriding is a type of polymorphism where multiple methods with the same name but different parameters can be defined.
Method overriding is a type of polymorphism where multiple methods with the same name but different parameters can be defined.
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An abstract class can be instantiated in Java.
An abstract class can be instantiated in Java.
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Study Notes
Object-Oriented Programming in Java
Classes and Objects
- A class is a blueprint for creating objects
- A class defines the properties and behaviors of an object
- An object is an instance of a class, with its own set of attributes (data) and methods (functions)
Inheritance
- Inheritance is the process of creating a new class based on an existing class
- The new class (subclass) inherits the properties and behaviors of the existing class (superclass)
- A subclass can also add new properties and behaviors or override the ones inherited from the superclass
Polymorphism
- Polymorphism is the ability of an object to take on multiple forms
- This can be achieved through method overriding or method overloading
- Method overriding: a subclass provides a specific implementation of a method already defined in its superclass
- Method overloading: multiple methods with the same name but different parameters can be defined
Encapsulation
- Encapsulation is the concept of bundling data and methods that operate on that data within a single unit (a class)
- This helps to hide the implementation details of an object from the outside world and provides a way to control access to the data
Abstraction
- Abstraction is the concept of showing only the necessary information to the outside world while hiding the implementation details
- In Java, abstraction is achieved through abstract classes and interfaces
- Abstract classes: a class that cannot be instantiated and is used as a base class for other classes
- Interfaces: a collection of abstract methods that must be implemented by any class that implements it
Composition
- Composition is the concept of creating objects from other objects
- In Java, composition is achieved through container classes that hold references to other objects
Access Modifiers
- Access modifiers (public, private, protected) control the accessibility of classes, methods, and variables
- Public: accessible from anywhere
- Private: accessible only within the same class
- Protected: accessible within the same class and its subclasses
Object-Oriented Programming in Java
Classes and Objects
- A class is a blueprint for creating objects, defining properties and behaviors
- Objects are instances of a class, with unique attributes (data) and methods (functions)
Inheritance
- Creates a new class based on an existing class (superclass)
- Subclass inherits properties and behaviors from superclass
- Subclass can add new properties and behaviors or override inherited ones
Polymorphism
- Ability of an object to take on multiple forms
- Achieved through method overriding or method overloading
- Method overriding: subclass provides a specific implementation of a superclass method
- Method overloading: multiple methods with same name but different parameters
Encapsulation
- Bundles data and methods that operate on that data within a single unit (class)
- Hides implementation details from the outside world
- Controls access to data through methods
Abstraction
- Shows only necessary information to the outside world
- Hides implementation details
- Achieved through abstract classes and interfaces
- Abstract classes: cannot be instantiated, used as base classes for others
- Interfaces: collection of abstract methods that must be implemented
Composition
- Creates objects from other objects
- Container classes hold references to other objects
Access Modifiers
- Control accessibility of classes, methods, and variables
- Public: accessible from anywhere
- Private: accessible only within the same class
- Protected: accessible within the same class and its subclasses
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Description
Learn about the basics of object-oriented programming in Java, including classes, objects, and inheritance. Understand how to create classes, define properties and behaviors, and use inheritance to create new classes.
