1.- about the java technology.pptx

8/11/2019 1.- About the Java Technology.pptx

1/25

About the Java Technology

Copyright 1995, 2011 Oracle and/or its affiliates. All rights reserved.

Adriana Rojas Molina

Agosto- Diciembre 2014


2/25

Java Technology

Java technology is :

A Programming language

A platform

The Java programming language:

High-level language characterized by the following

buzzwords

Simple Architecture

neutral

Object oriented Portable Dynamic

Distributed High

performance

Multithreaded Robust Secure


3/25

Simple, Objected Oriented

Simple: Fundamental concepts are grasped

quickly

Without extensive programmer training

Objected Oriented: Object technology had

been in the world since thirty years ago


4/25


5/25

Architecture Neutral, Portable

Architecture Neutral: Java technology is

designed to support applications that will be

deployed into heterogeneous network

environments

Portable: Your programs are the same on

every platform (there are no data type

incompatibilities across hardware and

software)


6/25

High performance

The java platform achieves superior

performance by adopting a scheme by with

the interpreter can run at full speed without

needing to check the run-time enviroment.


7/25

Threaded, Dynamic

A user working with HotJava Browser can run

several animations concurrently while

downloading an image an scrolling the page.

Multithreading capability means to build

applications with many concurrent threads of

activity

The language and rutime system are dynamic

in their linking stages.


8/25

Being familiar with the java technology

(1/2)

Al source code is first written in plain text files ending with

the .java extension.

.java files are then compiled into .class files by the javac

compiler. A .class file does not contain code that is native to

your processor, it instead contains bytecodesthe machine

language of the Java Virtual Machine). The java laucher tool

then runs your application with an instance of the JVM


9/25

Java VM is available on many

different operating systems so

the same .class files are capable

of running on Windows, Solaris,

Linux, Mac OS.

Some virtual machines (Java

HotSpot virtual machine),

perform additional steps at

runtime to give yourapplication a performance

boost.

Being familiar with the java technology

(2/2)


10/25

The Java Platform

Aplatformis the HW or SW environment in which

a program runs (popular platforms are Windows,

Linux, Solaris OS, Mac OS). Most platforms can be

described as a combination of the operatingsystem and underlying hardware.

The Java platform differs from most otherplatforms because its a software-only platform


11/25

The Java platform

Java platform has two components Java Virtual Machine (the base of

the Java Platform)

Java Application Programming

Interface (API). The API is a large

collection of ready-made

software components that

provide many useful capabilities.

It is grouped into libraries of

related classes and interfaces;

these libraries are known as

packages


12/25

Object-Oriented Programming

Concepts

What is an Object?

What is a Class?

What is Inheritance?

What is a Package


13/25

What is an Object? 1/3

Look around right now and youll find many examples of real-

world objects (your dog, your desk, your bicycle)

Real-world object share two characteristics: state(name, color, hungry)

behavior (barking, fetching, wagging tail)

Take a minute right now to observe the real-world objectsthat next to you. For each object, ask yourself two questions:

What possible states can this object be in? What possible

behavior can this object perform?


14/25

What is an Object? (2/3)

Software objects are similar to real-world objects, they too consist of

state and related behavior.

Objects store its state infields(variables

in some programming languages) Objects exposes its behavior through

methods(functions in some

programming languages)

Methodsoperate on an objects internal

state and serve as the primarymechanism for object-to-object

communication.

Hiding internal state and requiring all

interaction to be performed through an

objects method is known as dataencapsulation


15/25

What is an Object? (3/3)

Using software objects provide the following

benefits:

Modularity: Source code for an object can be written and

maintained independently of the source code for otherobjects

Information-hiding: The detail of its internal

implementation remain hidden from the outside world

Code re-use: If an object already exists, you can use thatobject in your program


16/25

What is a Class? (1/3)

In the real world, youll often find many individual objects all

of the same kind. There may be thousands of other bicycles in

existence, all of the same model and make.

Each bicycle was built from the same blueprints and therefore

contains the same components

In object-oriented terms, we say that your bicycle is an

instanceof the class of objectsknown as bicycles.

A classis the blueprint from which individual objects arecreated


17/25

What is a Class? (2/3)

Check the following Bicycle class

class Bicycle {

int cadence = 0;

int speed = 0;

int gear = 1;

void changeCadence(int newValue) {

cadence = newValue; }

void changeGear(int newValue) {

gear = newValue; }

void speedUp(int increment) {

speed = speed + increment; }

void applyBrakes(int decrement) {

speed = speed - decrement; }

void printStates() {

System.out.println("cadence:"+cadence+" speed:"+speed+" gear:"+gear);}


18/25

What is a class? (3/3)

Here is a BicycleDemoclass that creates two separate Bicycle

objects and invokes their methods:

class BicycleDemo {

public static void main(String[] args) {

// Create two different Bicycle objects

Bicycle bike1 = new Bicycle();

Bicycle bike2 = new Bicycle();

// Invoke methods on those objects

bike1.changeCadence(50);

bike1.speedUp(10);

bike1.changeGear(2);bike1.printStates();


bike2.speedUp(10);

bike2.changeGear(2);


bike2.speedUp(20);

bike2.changeGear(3);

bike2.printStates(); }

}


19/25

What is Inheritance? (1/3)

Different kinds of objects often have a certain amount in

common with each other. Mountain bikes, road bikes and

tandem bikes, for example all share the characteristics of

bicycles. Yet each also defines additional features that make

them differente: tandem bicycles: two seats & two sets of handlebars

road bikes : drop handlebars

mountain bikes: additional chain ring giving them a lower gear ratio

Object-oriented programming allow classes to inheritcommonly used state and behavior from other classes.

Bicyclebecomes a superclassof MountainBike, RoadBike, and

TandemBike


20/25


In Java programming language, each class is allowed to have

one direct superclass and each superclasshas the potential

for an unlimited number of subclasses


21/25


The syntax for creating a subclass is simple. At the beginning

of your class declaration, use the extendskeyword, followed

by the name of the class to inherit from:

class MountainBike extendsBicycle {

// new fields and methods defining a mountain bike would go here

}

This gives MountainBikeall the same fields and methods as

Bicycle, yet allows its code to focus exclusively on the featuresthat make it unique.


22/25

What is an Interface?

As you ve already learned, objects define their interaction with theoutside world through the methods that they expose.

Methods form the objects interfacewith the outside world.

In its most common form, an interface is a group of related methods with

empty bodies.

A bicycles behavior, if specified as an interface, migh appear as follows:interface Bicycle {

void changeCadence(int newValue); // wheel revolutions p/m

void changeGear(int newValue);

void speedUp(int increment);

void applyBrakes(int decrement);

}

Implementing an interface allows a class to become more formal about

the behavior it promises to provide. Interfaces form a contract between

the class an the outside world, and this contract is enforced at build time

by the compiler.


23/25

What is a Package?

A package is a namespace that organizes a set of related classes and

interfaces. Conceptually you can think of packages as being similar to

different folders on your computer. You might keep HTML pages in one

folder, images in another, and scripts or applications in yet another.

As software written in the Java programming language can be composed

of hundreds or thousands of individual classes , it makes sense to keep

things organized by placing related classes and interfaces into packages

The Java platfom provides an enormous class library (a set of packages)

suitable for use in your own applications. This library is known as the

ApplicationsProgramming Interface(API)


24/25

Questions

1. Real-world objects contain ____ and ____.

2. A software objects state is stored in ____.

3. A software objects behavior is exposed through ________.

4. Hiding internal data from the outside world, and accessing it only through publiclyexposed methods is known as data _______

5. A blueprint for a sofware object is called a ____

6. Common behavior can be defined in a___ and inherited into a ____ using the _____

keyword

7. A collection of methos with no implementation is called an ______.

8. A namespace that organizes classes and interfaces by functionality is called a ____

9. Ther term API stands for ____?


25/25

Bibliografa

http://download.oracle.com/javase/tutorial/java/concepts/index.html

1.- about the java technology.pptx

Documents