Library classes

Class creation

• User defined (if the user creates)

• Library classes (Readily available with the system)

LIST OF LIBRARY CLASSES

• Java.io

• Java.lang

• Java.awt

• Java.util

• Java.applet

• Java.net

• Java.math

Input operations in java

• System.in.read();

• In.readLine();

Output operations in java

• System.out.print();

• System.out.println();

Types of streams

Input stream related to keyboardInput stream related to keyboard• System.in

Output stream related to VDUOutput stream related to VDU• System.out• System.err

These streams are available in java.io

Categories of stream

• Character related

Referred as reader stream and writer stream (for character encoding)

• Byte related

Any data in terms of byte can be inputted

Exception & Exception handling

• An unexpected situation which occurs due to improper use of input resources during the execution of the program

• The process of eliminating unexpected errors during runtime

TRY and CATCH

Try contains block of statements to perform

An error will be trapped in try block

Hence try is an error trapper

Catch will be informed about the error and catch the errors

Throws Keyword

Applied with the function signature

Throws IOException

If error occurs it will report to the error handler

Wrapper classes

• It is a member of java library

• It wraps the primitive data type in an object

Need of Wrapper class

• To store primitive values in objects as well as in conversion from string to primitive types

• Ex :

• String x = “12”;

• int c =Integer.parseInt(x);

Static data members

• Instant variables which is global in the class and used commonly by all the objects of that class

Static member methods

• Method which uses only static data members or static instant variables

Packages in java

• It is a group of class which can be imported to a program to use implicit facilities

• It can be included by using import keyword

• A package may be defined by the user and is termed as user defined packages