OOP

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• Abstraction
• Encapsulation
• Inheritance
• Polymorphism

Key words: Abstract Class vs Interface

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Encapsulation Hiding internal state and requiring all interaction to be performed through an object's methods is known as data encapsulation.

https://docs.oracle.com/javase/tutorial/java/concepts/object.html

Encapsulation in Java:

• Restricts direct access to data members (fields) of a class.
• Fields are set to private
• Each field has a getter and setter method
• Getter methods return the field
• Setter methods let us change the value of the field

https://raygun.com/blog/oop-concepts-java/

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Inheritance Object-oriented programming allows classes to inherit commonly used state and behavior from other classes.

https://docs.oracle.com/javase/tutorial/java/concepts/inheritance.html

Inheritance in Java:

• A class (child class) can extend another class (parent class) by inheriting its features.
• Implements the DRY (Don’t Repeat Yourself) programming principle.
• Improves code reusability.
• Multilevel inheritance is allowed in Java (a child class can have its own child class as well).
• Multiple inheritances are not allowed in Java (a class can’t extend more than one class).

https://raygun.com/blog/oop-concepts-java/

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Abstraction Abstraction aims to hide complexity from the users and show them only the relevant information.

Abstraction in Java:

• Hides the underlying complexity of data
• Helps avoid repetitive code
• Presents only the signature of internal functionality
• Gives flexibility to programmers to change the implementation of the abstract behaviour
• Partial abstraction (0-100%) can be achieved with abstract classes
• Total abstraction (100%) can be achieved with interfaces

https://raygun.com/blog/oop-concepts-java/

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Polymorphism Polymorphism refers to the ability to perform a certain action in different ways.

Polymorphism in Java:

• The same method name is used several times.
• Different methods of the same name can be called from the object.
• All Java objects can be considered polymorphic (at the minimum, they are of their own type and instances of the Object class).
• Example of static polymorphism in Java is method overloading.
• Example of dynamic polymorphism in Java is method overriding.

https://raygun.com/blog/oop-concepts-java/

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Interface An interface is a contract between a class and the outside world. When a class implements an interface, it promises to provide the behavior published by that interface.

https://docs.oracle.com/javase/tutorial/java/concepts/index.html