Packages in java

1)        java.lang: - This package got primary classes and interfaces essential for java program. It consists of wrapper classes, strings, threads, etc. wrapper classes are useful to create an object. Thread means process.

à java.lang package by default import in to every java  program.

2)        java.util: - (utility) in this util data structures are available. This package contains useful classes and interfaces like stack, linked list, hash table, arrays. etc.

3)        java.io: - This package handles files and input output related tasks. (io – input output).

4)        java.awt : - abstract window tool kit.

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

Java.awt.event à event is useful to providing actions.

GUIà graphics user interface.

5)        javax.swing: - This package helps to develop GUI like java.awt.  X means extended.  This package is developed from another package.

6)        java.net: - Client – server programming can be done using this package. Net stands for network.

7)        java.applet: - applets are programs which come from a server into a client and get executed on the client machine.  An applet is a program that comes to the internet server.

8)        java.sql: - structured query language.  This package helps to connect to database like oracle and utilize them in java.  A data base is a storage data.

à A variable is memory location to store data.  Int represent you can store integer numbers. Numbers are without decimal points. It is a data type.