mowi Lesson: Object-Oriented Programming
Concepts
If you've never used an object-oriented
programming language before, you'll
need
to learn a few basic concepts before you
can begin writing any code. This lesson
will
introduce you to objects, classes,
inheritance, interfaces, and packages.
Each
discussion focuses on how these
concepts
relate to the real world, while
simultaneously providing an
introduction to
the syntax of the Java programming
language.
What Is an Object?
An object is a software bundle of related
state and behavior. Software objects are
often used to model the real-world
objects
that you find in everyday life. This lesson
explains how state and behavior are
represented within an object, introduces
the concept of data encapsulation, and
explains the benefits of designing your
software in this manner.
What Is a Class?
A class is a blueprint or prototype from
which objects are created. This section
defines a class that models the state and
behavior of a real-world object. It
intentionally focuses on the basics,
showing
how even a simple class can cleanly
model
state and behavior.
What Is Inheritance?
Inheritance provides a powerful and
natural mechanism for organizing and
structuring your software. This section
explains how classes inherit state and
behavior from their superclasses, and
explains how to derive one class from
another using the simple syntax
provided
by the Java programming language.
What Is an 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. This section defines a simple
interface and explains the necessary
changes for any class that implements it.
What Is a Package?
A package is a namespace for
organizing
classes and interfaces in a logical
manner.
Placing your code into packages makes
large software projects easier to
manage.
This section explains why this is useful,
and
introduces you to the Application
Programming Interface (API) provided
by
the Java platform.
Questions and Exercises: Object-
Oriented
Programming Concepts
Use the questions and exercises
presented
in this section to test your
understanding of
objects, classes, inheritance, interfaces,
and
packages.
Trail: Learning the Java Language
This trail covers the fundamentals of
programming in the Java programming
language.
Object-Oriented Programming
Concepts teaches you the core
concepts behind object-oriented
programming: objects, messages,
classes,
and inheritance. This lesson ends by
showing you how these concepts
translate
into code. Feel free to skip this lesson if
you are already familiar with object-
oriented programming.
Language Basics describes the
traditional features of the language,
including variables, arrays, data types,
operators, and control flow.
Classes and Objects describes how to
write the classes from which objects
are created, and how to create and use
the
objects.
Interfaces and Inheritance describes
interfaces—what they are, why you
would want to write one, and how to
write
one. This section also describes the way
in
which you can derive one class from
another. That is, how a subclass can
inherit
fields and methods from a superclass .
You
will learn that all classes are derived
from
the Object class, and how to modify the
methods that a subclass inherits from
superclasses.
Numbers and Strings This lesson
describes how to use Number and
String objects The lesson also shows you
how to format data for output.
Generics are a powerful feature of the
Java programming language. They
improve the type safety of your code,
making more of your bugs detectable at
compile time.
Packages are a feature of the Java
programming language that help you
to organize and structure your classes
and
their relationships to one another.