Java package: Difference between revisions

Revision as of 18:00, 5 January 2006

Revision as of 09:43, 8 January 2006

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Java Source Files belonging to the same category or provide similar functionality can be packed into a Java Package. Java Packages are stored in compressed files called [[Jar (file format)|jar]] Files. Inside the package the files can be stored hierachically, therefore it is possible to combine several subdirectories into one package.

Related [[Datatype|types]] in Java are placed in a common package.

*A package provides a unique [[namespace|namespace]] for the types it contains.

*A package facilitates access protection.

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**Annotations

ATo use a package isinside represented ina Java codeSource byFile, ait seriesmust ofbe textualimported names delimited bywith the '.' (dot)import character.statement,

e.g. import java.awt.event.*;

e.g

import java.awt.event.*;

This imports all files from the directory java/awt/event

==Packages in Java 1.5==

* java.lang, java.util: These packages provide basic language functionality like regular expressions, the Reflection API

* java.math: provides mathematical functions

* New I/O: the new I/O framework for Java

* I/O: File Operations

* Networking: Networking Operations, Sockets, DNS lookups,...

* Security: key generation, encryption and decryption

* Java Database Connectivity (JDBC): to access databases

* Java AWT: set of packages for GUI

* Java Swing: native Java GUI components

== Creation of Jar Files==

In the Java Source Files the package the file shall belong to must be specified with the package keyword, e.g.

/package java/.awt/.event

Jar Files are created with the jar command-line utility. The command

And is stored on disk {or in a compressed file such as a [[Jar (file format)|jar]] or Ear (Enterprise Archive)}

as a series of nested directories.

e.g.

/java/awt/event

jar cf myPackage.jar *.class

compresses all *.class files into the Jar File myPackage.tar.

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