Web Browser1

7/31/2019 Web Browser1

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using

JAVA

WEB BROWSER


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Application and applet

An application is a standalone javaprogram. Every standalone applicationhas the main() method.

An applet is a program that can betransmitted over the internet. It haslimited access to clients resources.


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Secure

When you use a Java-compatible Webbrowser, you can safely download Java

applets without fear. Java achieves thisprotection by confining a Java programto the Java execution environment andnot allowing it

access to other parts of the computer


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Multithreaded

Java supports multitasking bysupporting multithreading. Thread is aline of execution.

When a process is sub divided into anumber of sub processes and each subprocess is assigned a separate thread,it

is called multithreading.


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Architecture neutral

The java source code is first compiledinto bytecode. Then this bytecode isinterpreted by the java virtual machine.

There are separate jvm for differentplatforms therefore same source codecan run on different platforms


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8/19/12 Javas bytecode concept


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Portable

The java source code can be run on anyplatform that is why it is also portablein nature.


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OOP Principles

1. Encapsulation2. Inheritance

3. Abstraction

4. Polymorphism


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Encapsulation

Encapsulation is the mechanism thatbinds together code and the data itmanipulates,

and keeps both safe from outsideinterference and misuse


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Inheritance

Inheritance is the process by which oneclass acquires the properties of anotherclass.

We use the keyword import to supportinheritance.


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Class a extends b

{

}

A is the subclass and b is the

superclass.


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Abstraction

It is the art of giving the importantinformation without giving thebackground details.


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Polymorphism

It is a greek word that means manyforms.

A method in java can be overloaded oroverridden as per requirement and thuscan exist in more than one form.


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8/19/12Concept of Class & Method


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GRAPHICAL USER INTERFACE

AN INTRODUCTION.


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Awt and swing

Awt stands for application windowtoolkit.it is a class that is used to creategraphical applications.

Swing is also a built in java class that isused to create graphical applications.


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All the entities that you see on yourwindow are called components.whenever these components are

clicked they give rise to events.

Events are Java objects that areinstantiated by the component and

passed as an argument to any listeners.


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A listener of an event registers itselfwith the source of the event. When anevent occurs, the source of the event

invokes a method on the listener.The interface contains the methods

that the listener must implement and

that the source of the event invokeswhen the event occurs.


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DESCRIPTION

OF THESOURCE CODE


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import java.awt.*;

import java.awt.event.*;

import java.util.*;

import java.io.*;

import javax.swing.*;

import javax.swing.event.*;

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THE IMPORT KEYWORD IS USED TO USETHE INBUILD JAVA PACKAGES

import javax.swing.*;

import javax.swing.event.*;

THE AWT AND SWING PACKAGES ARE USED TOCREATE GRAPHICAL APPLICATIONS AND THEAWT.EVENT AND SWING.EVENT ARE USED TOINCLUDE EVENT HANDLING.

import java.awt.*;import java.awt.event.*;

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public classWebBrowser

{

public staticvoid main(String[] args)

{

JFrameframe = newEditorPaneFrame();

A public class iscreated namedWebBrowserwhich containsthe main()

function.

A frame is createdand the show

method is invokedon it.

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classEditorPaneFrameextends JFrame

{

privateJTextField url;

privateJCheckBox

editable;

private JButton

loadButton;

A classEditorPaneFrameis created thatextends the class

Jframe.

A textfield namedurl, a checkboxnamed editable,

two buttonsnamed loadbuttonand backButton

and an editorPaner l r .

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publicEditorPaneFrame()

{

setTitle("Java WebBrowser");

setSize(600,400);

addWindowListener(new

WindowAdapter()

The constructorfor theEditorPaneFrameclass is created.

The title of theweb browserframe is set.

The size of theweb browser isset.

The windowlistener for the

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url = new JTextField(30);

loadButton = new JButton("Load");

loadButton.addActionListener(new

ActionListener()

{

public voidactionPerformed(ActionEvent event)

{

try

{

// remember URL for back button

urlStack.push(url.getText());

editorPane.setPage(url.getText());

}

catch(Exception e)

{

editorPane.setText("Error: " +e);

}

A text field and abutton named urland LoadButtonrespectively arecreated.

Event listener forthe LoadButton iscreated.

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backButton = new JButton("Back");

backButton.addActionListener(newActionListener()

{

public voidactionPerformed(ActionEvent event)

{

if(urlStack.size()


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editorPane = newJEditorPane();

editorPane.setEditable(false);

editorPane.addHyperlinkListener(ne

wHyperlinkListener()

{

An EditorPane iscreated and therequired eventlistener isregistered for it.

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editorPane = newJEditorPane();

editorPane.setEditable(false);

editorPane.addHyperlinkListener(ne

wHyperlinkListener()

{

An EditorPane iscreated and therequired eventlistener isregistered for it.

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editable = newJCheckBox();

editable.addActionListener(new

ActionListener() {

public

voidactionPerformed(ActionEvent

event)

A checkboxnamed editable iscreated and theevent listener forit is registered.

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ContainercontentPane =getContentPane();

contentPane.add(

newJScrollPane(editor

Pane), "Center");

JPanel panel= new JPanel();

A contenetPane iscreated and ascrollPane isadded to it.

A panel is

created.Two labels (URL

and editable) and

the componentsthat were createdbefore (two

button, a

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8/19/12JVM

8/19/12execut ng t e yte co e to get t e


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8/19/12execut ng t e yte co e to get t eoutput..

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8/19/12web browser(output)

Web Browser1

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