Examplets from The Java Developers Almanac 2000 docx

Legal Terms Examplets SM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan... }; } } Examplets TM provided by permission of the publisher, Addision-Wesle

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"Examplets" are code snippets that illustrate a particular task.

They're designed to show which classes and members areinvolved in performing the task, and how the classes andmembers interact with each other You will see blue italicizedtext in an examplet; this indicates code that should be replaced

if you use it in your program

An examplet can have enough detail for you to use it, as is Oryou might have to get more information about the involvedclasses A good place to find information about the Java 2Platform APIs is the Java 2 Platform API index

It's also good practice to add catch clauses, as appropriate, tothe examplets If the code of an examplet throws a checkedexception, the code is surrounded by a try/catch statement

However, to reduce space and distraction, the catch clause isleft blank Catch clauses should always handle the exceptionand should never be left blank So, at the very least, youshould include a call to e.printStackTrace() to display the exception

on the console

You'll find examplets in a variety of categories See the Table ofContents for a list of categories, and the examplets in eachcategory

Table of Contents

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CompressionJAR filesDatabase - JDBCData Structures and AlgorithmsFiles, Streams, I/O

ImagesInternationization

JNDIDirectoryEventLdapMathNetworkingPrintingReference ObjectsReflection

RMISecuritySoundSampledMidiStringsSwingEventsFile ChooserLayout

TreeTextThreadsTimejavax.rmijavax.swing.undo

(java.util.jar)(java.sql)(java.util)(java.io)(java.awt.image)(java.text)

(java.beans)(javax.naming)(javax.naming.directory)(javax.naming.event)(javax.naming.ldap)(java.math)

(java.net)(java.awt.print)(java.lang.ref)(java.lang.reflect)(java.rmi)

(java.security)

(javax.sound.sampled)(javax.sound.midi)(java.lang)

(javax.swing)(javax.swing.event)(javax.swing.filechooser)(java.awt and javax.swing)(javax.swing.tree)

(javax.swing.text)(java.lang)

(java.lang)(javax.naming)(javax.naming.directory)(javax.naming.event)(javax.naming.ldap)(javax.rmi)

(javax.swing.undo)

http://developer.java.sun.com/developer/codesamples/ (2 of 13) [8/1/2000 7:46:26 AM]

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Setting a Keyboard Accelerator for a Menu Item

Applets (java.applet)

The Quintessential AppletGetting an Applet ParameterMaking the Browser Visit a URLShowing a Message in the Browser's Status BarLoading and Playing Audio in an Applet

Loading and Playing Audio in an ApplicationLoading and Painting an Image in an AppletAnimating an Array of Images in an Applet

AWT (Abstract Windowing Toolkit) (java.awt)

The Quintessential Drawing ProgramDrawing Basic Shapes

Filling Basic ShapesLoading an ImageDrawing an ImageScaling, Shearing, Translating, and Rotating a DrawnImage

Drawing Simple TextDrawing Rotated TextGetting the Dimensions of TextDrawing Anti-Aliased Text and GraphicsDrawing with Alpha

Setting the Clipping Area with a ShapeChanging the Thickness of the Stroking Pen

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Fonts (java.awt.font)

Listing All Available FontsDrawing a Paragraph of TextGetting the Shape from the Outline of TextDrawing Text with Mixed Styles

Shapes (java.awt.geom)

Creating a Shape with Lines and CurvesCreating Basic Shapes

Combining ShapesScaling, Shearing, Translating, and Rotating a Shape

Compression (java.util.zip)

Compressing a FileDecompressing a FileListing the Contents of a ZIP FileCalculating the Checksum of a Byte Array

JAR files (java.util.jar)

Retrieving the Manifest of a JAR File

Database - JDBC (java.sql)

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Creating a ListCreating a Hash TableTruncating a List

Converting a Collection to an ArrayConverting an Array to a CollectionImplementing a Queue

Implementing a StackIterating the Elements of a CollectionSorting an Array

Finding an Element in a Sorted ArrayFinding an Element in a Sorted ListInserting an Element into a Sorted ListGenerating a Random Number

Breaking a String into WordsReading Properties from a Properties FileCreating Date Object From a Particular DateParsing a Date Using a Pattern

Reading and Writing a Properties FileGetting and Setting Properties

Scheduling a Timer Task to Run at a Certain TimeScheduling a Timer Task to Run Repeatedly

Files, Streams, I/O (java.io)

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Listing the File System RootsSetting File Modification TimeSerializing an Object

Deserializing an ObjectTraversing a DirectoryReading UTF-8 Encoded DataWriting UTF-8 Encoded DataReading ISO Latin-1 Encoded DataWriting ISO Latin-1 Encoded Data

Images (java.awt.image)

Converting an Image to a Buffered ImageGetting Pixels from a Buffered ImageGetting a Sub-Image of an ImageCreating and Drawing on a Buffered ImageScaling, Shearing, Translating, and Rotating an ImageConverting a Color Image to Gray

Blurring an ImageSharpening an ImageEmbossing an Image

Internationization (java.text)

Formatting and Parsing a Locale-specific NumberFormatting and Parsing Locale-specific CurrencyFormatting and Parsing a Locale-specific PercentageFormatting and Parsing a Locale-specific Date

Formatting and Parsing Locale-specific TimeFormatting and Parsing a Locale-specific Date and TimeDetermining the Type of a Character

Comparing Strings in a Locale-independent WayDetermining the Character Boundaries in a Unicode StringDetermining the Word Boundaries in a Unicode StringDetermining the Sentence Boundaries in a Unicode String

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Math (java.math)

Operating With Big Integer ValuesOperating With Big Decimal ValuesSetting the Decimal Place of a Big Decimal Value

Networking (java.net)

Creating a URLParsing a URLReading Text from a URLCalling a CGI Using POST MethodResolving a Hostname

Creating a Client SocketCreating a Server SocketReading Text from a SocketWriting Text to a SocketSending a DatagramReceiving a DatagramJoining a Multicast GroupReceiving from a Multicast GroupSending to a Multicast Group

Printing (java.awt.print)

The Quintessential Printing ProgramGetting the Dimensions of a Printed PageSetting the Orientation of a Printed PagePrinting Pages with Different FormatsDisplaying the Page Format Dialog

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Invoking a Method Using a Method ObjectGetting the Modifiers of a Member ObjectGetting the Name of a Class or Member ObjectDetermining if an Object Is an Array

Determining the Dimensions of an ArrayGetting the Component Type of an ArrayCreating an Array

Expanding an ArrayGetting and Setting the Value of an Element in an ArrayOverriding Default Access

Creating a Proxy Object

RMI (java.rmi)

Starting Up the RMI RegistryDefining and Exporting a Remote ObjectLooking Up a Remote Object and Invoking a MethodPassing Parameters to a Remote Method

Returning Values from a Remote MethodThrowing an Exception from a Remote Method

Sound Sampled (javax.sound.sampled)

Loading and Playing Sampled AudioDetermining the File Format of a Sampled Audio FileDetermining the Encoding of a Sampled Audio FileDetermining the Duration of a Sampled Audio FilePlaying Streaming Sampled Audio

Continuously Playing a Sampled Audio FileDetermining the Position of a Sampled Audio PlayerDetermining When a Sampled Audio Player hasFinished Playing

Controlling the Volume of Playing Sampled Audio

Midi

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Creating a New Key Pair and Self-signed CertificateCreating and Signing a JAR File

Creating a New Policy FileManaging Policy FilesCreating a Keyed Digest Using MD5Getting a Certificate from a KeystoreChecking Read/Write Permission for a DirectoryChecking if One Permission Implies AnotherCreating a Secure Random Number

Creating Image Radio ButtonsRetrieving the Selected Button in a GroupFiring Item Events

Creating a File Chooser DialogDisplaying Only Directories in a File Chooser DialogCreating an Internal Frame

Creating a List ComponentCreating a Scrolling List ComponentSetting the Selection Mode of a List Component

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Showing a Dialog BoxCreating Key Strokes and Binding Them to ActionsAdding an InputMap to a Component

Setting a Tool TipLaying Out Components in a Row or ColumnSeparating Components in a Row or ColumnLaying Out Components in a Flow (Left-to-Right,Top-to-Bottom)

Laying Out Components in a GridLaying Out Components Using Absolute CoordinatesSetting a Border

Adding a Title to a BorderCreating a Compound BorderDetermining the Available Look and FeelsSetting the Look and Feel

Painting the Background of a Container with an ImagePattern

Events (javax.swing.event)

Handling Hyperlink EventsHandling Changes to a List Component

File Chooser (javax.swing.filechooser)

Adding a Filter to a File Chooser Dialog

Tree (javax.swing.tree)

Creating a TreeHandling Selection Events in a Tree Component

Text (javax.swing.text)

Inserting Styled Text in a Text PaneInserting an Image into a Text PaneInserting a Component into a Text Pane

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Replacing Substrings in a StringConverting a String to Upper or Lower CaseConverting a String to a Number

Shifting Elements in an ArrayCopying Elements from One Array to AnotherRetrieving the SuperClass of an Object

Getting the Package of an ObjectImplementing a Work QueueExecutes a Command

Reading Output from a CommandSending Input to a CommandPausing

Getting the Current TimeGetting the Value of a System PropertySetting the Value of a System PropertyUsing a Thread-local Variable

Loading Native CodeConverting Unicode to UTF-8Converting UTF-8 to UnicodeDetermining a Character's Unicode Block

JNDI

Creating an Initial Context to the Naming ServiceLooking Up an Object From the Naming ServiceListing a Context in the Naming Service

Adding, Replacing, Removing, and Renaming a Binding inthe Naming Service

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Getting an Object's Schema from the DirectoryGetting an Attribute's Schema from the DirectoryAuthenticating to the Directory

Performing an LDAP ``Extended'' Operation

javax.rmi

Starting the Name ServerDefining and Exporting a Portable Remote ObjectLooking Up a Portable Remote Object and Invoking aMethod

javax.swing.undo

Adding Undo and Redo to a Text Component

These code examples and other materials are subject to Sun Microsystems, Inc Legal Terms

Examplets SM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan.

[ This page was updated: 31-Jul-2000 ]

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The Quintessential Accessible Object

You should try to subclass from JComponent or one of itsdescendents since that will automatically make your objectaccessible If that is not possible, your object should implementAccessible

import javax.accessibility.*;

public class BasicAccessible implements Accessible { public AccessibleContext getAccessibleContext() { return new AccessibleContext() {

// Implement all the abstract methods in this // abstract class

};

} }

Examplets TM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan.

Order this book from Amazon

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Setting an Accessible Name for an Image Button

You should also set the accessible name for components that onlyshow an image The tool tip text, if set, serves as the accessiblename for a component However, if the tool tip text is being used forsomething else, set the component's accessible name

// If tool tip is being used for something else, // set the accessible name

button.getAccessibleContext().setAccessibleName(

"Button Name");

FAQ | Feedback | Map | A-Z Index For more information on Java technology

and other software from Sun Microsystems, call:

(800) 786-7638

Outside the U.S and Canada, dial your country's

AT&T Direct Access Number first.

http://developer.java.sun.com/developer/codesamples/javax.accessibility/175.html [8/1/2000 7:46:39 AM]

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Setting a Description for Image Icons

Image icons can be inserted in a variety of places such as in a text

or tree component You should set a description for image icons tohelp blind users

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Setting a Mnemomic for Buttons

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Setting a Mnemonic for a Menu

At least one menu in a menu bar should have a mnemonic Thismakes all the menus and menu items accessible

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Associating a Label with a Component

When a label is associated with a component, you should callsetLabelFor() to make the association explicit and then set amnemonic on the label The associated component will get thefocus when the mnemonic is activated

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Setting a Keyboard Accelerator for a Menu Item

At least one menu in a menu bar should have a mnemonic Thismakes all the menus and menu items accessible

//The next two lines should be in one line

item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent

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The Quintessential Applet

Every applet must subclass Applet

import java.applet.*;

import java.awt.*;

public void init() { // Called once by the browser when // it starts the applet

} public void start() { // Called whenever the page containing // this applet is made visible

} public void stop() { // Called whenever the page containing this // applet is not visible

} public void destroyed() { // Called once when the browser destroys // this applet

} public void paint(Graphics g) { // Called whenever this applet needs to // repaint itself

} }

This is the applet's accompanying HTML file

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Getting an Applet Parameter

Here is a sample HTML file containing a value for the parameter

\meta{p}

</applet>

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Making the Browser Visit a URL

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http://developer.java.sun.com/developer/codesamples/java.applet/2.html [8/1/2000 7:46:47 AM]

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Showing a Message in the Browser's Status Bar

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Loading and Playing Audio in an Applet

// The following 2 lines of code must be // on the same line

AudioClip ac = getAudioClip(getDocumentBase(), "http://hostname/audio.au");

ac.play();

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Loading and Playing Audio in an Application

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Loading and Painting an Image in an Applet

}Examplets TM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan.

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Animating an Array of Images in an Applet

This is the simplest applet to animate an array of images Inpractice, you should use double-buffering (which this example doesnot use) to eliminate ``flickering.''

images[1] = getImage(getDocumentBase(),

} public void start() { (thread = new Thread(this)).start();

} public void stop() { thread = null;

} public void paint(Graphics g) {

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http://developer.java.sun.com/developer/codesamples/java.applet/7.html (2 of 2) [8/1/2000 7:46:56 AM]

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The Quintessential Drawing Program

This example creates a frame and draws an oval within the frame

import java.awt.*;

import javax.swing.*;

public void paint(Graphics g) { Graphics2D g2d = (Graphics2D)g;

getSize().height-1);

} public static void main(String[] args) { JFrame frame = new JFrame();

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Drawing Basic Shapes

There are two ways to draw basic shapes like lines and rectangles.The first is to use specific drawing methods like

Graphics.drawOval() This example uses these methods Thesecond is to construct a shape and then use Graphics2D.draw() todraw the shape See the java.awt.geom package for examples thatcreate shapes

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http://developer.java.sun.com/developer/codesamples/java.awt/9.html [8/1/2000 7:46:58 AM]

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Filling Basic Shapes

There are two ways to fill basic shapes like lines and rectangles.The first is to use specific drawing methods like Graphics.fillOval().This example uses these methods The second is to construct ashape and then use Graphics2D.fill() to fill the shape See thejava.awt.geom package for examples that create shapes

Polygon polygon = new Polygon();

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imageIcon.paintIcon(this, g, x, y);

}Examplets TM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan.

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Scaling, Shearing, Translating, and Rotating a Drawn Image

AffineTransform tx = new AffineTransform();

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Drawing Simple Text

// Set the desired font if different from default font

// Draw the string such that its base line is at x, y

// Draw the string such that the top-left corner // is at x, y

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Drawing Rotated Text

// Draw string rotated clockwise 90 degrees

AffineTransform at = new AffineTransform();

at.setToRotation(Math.PI/2.0);

// Draw string rotated counter-clockwise 90 degrees

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Getting the Dimensions of Text

// From within the paint() method

public void paint(Graphics g) { Graphics2D g2d = (Graphics2D)g;

FontMetrics fontMetrics = g2d.getFontMetrics();

int height = fontMetrics.getHeight();

} // From within a component

MyComponent() {

FontMetrics fontMetrics = getFontMetrics(font);

int height = fontMetrics.getHeight();

} }Examplets TM provided by permission of the publisher, Addision-Wesley, and Author Patrick Chan.

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Drawing Anti-Aliased Text and Graphics

// Text only

RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

// Text and graphics

RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

drawGraphics(g2d);

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Drawing with Alpha

drawGraphic1(g2d);

// Set alpha 0.0f is 100% transparent and 1.0f is // 100% opaque

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Setting the Clipping Area with a Shape

drawGraphics(g2d);

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Tiêu đề	Examples from The Java Developers Almanac 2000
Năm xuất bản	2000

Định dạng
Số trang	364
Dung lượng	6,23 MB