Java Packages

A package in Java is an encapsulation mechanism that can be used to group related classes,interfaces, and sub-packages.

The dot (.) notation is used to uniquely identify package members in the package hierarchy. 

Declaring a package:

A package hierarchy represents an organization of the Java classes and interfaces. It does not represent the source code organization of the classes and interfaces. 

package syntax has the following syntax.

package <package name>;

Using a packages:

The accessibility of types (classes and interfaces) in a package may deny access from outside the package.

The import declarations must be the first statement after any package declaration in a source file. The simple form of the import declaration has the following syntax:

import < type name>;

Important packages in Java:

java.lang:

This package got primary classes and interfaces essential for java language. It consists

of wrapper classes, Strings, Threads etc. This package is by default imported into

every java program.

java.util:

This package contains useful classes and interfaces like stack, linkedlist, hashtable etc

java.io:

This package handles files and input /output related tasks.

jawa.awt:

This package helps to develop GUI. It consists of an important sub package

java.awt.event

javax.swing:

This package helps to develop GUI like java.awt

java.net:

client-server programming can be done using this package

java.applet:

Applets are programs which come from a server into a client and get executed on client machine.

java.sql:

This package helps to connect to databases like oracle and utilize them in java.