Polymorphism

Inheritance

The ability of a class to acquire properties and methods from another class

Base class (superclass)

The original class that is inherited from

Derived class (subclass)

A class that inherits from another class

Is-a relationship

A relationship where one class is a type of another class

Has-a relationship

A relationship where a class contains another class as a field

Polymorphism

The ability for different objects to respond differently to the same method call

Abstract class

A class that cannot be instantiated and may include methods without implementation

Abstract method

A method declared without a body that must be implemented later

Interface

A structure that defines methods a class must implement

extends

Keyword used to inherit from another class

implements

Keyword used when a class uses an interface

super

Keyword used to refer to the parent class

Overriding

Providing a new implementation of an inherited method

compareTo()

A method used to compare two objects for ordering

Comparable

An interface that requires objects to be comparable

java.lang

A default package containing core Java classes

Is-a relationship

A type of relationship that represents inheritance

Has-a relationship

A type of relationship that represents composition

Methods available to a subclass object

All public methods from a parent class plus additional methods

Abstract method

A method with no implementation

Overriding

A method that replaces an inherited method’s behavior

Interface

Can be used multiple times by a class

Abstract class

Can only be extended once

Extending a class syntax

class Subclass extends Superclass {}

Implementing an interface syntax

class MyClass implements InterfaceName {}

Abstract class syntax

abstract class ClassName {}

Abstract method syntax

public abstract void methodName();

Interface syntax

interface InterfaceName {}