7/30/2019 Package Part 1

1/23

Programming Language(JAVA)

Unit 6.9 In-built Packages

Presentation1

7/30/2019 Package Part 1

2/23

Revision

1. Define Inheritance.

2. List the types of Inheritance allowed in

java.

3. Explain method overriding.

7/30/2019 Package Part 1

3/23

Objectives

At the end of this presentation, you will be ableto

Define package and its types

List the advantages of packages

List some of the in-built packages in Java

7/30/2019 Package Part 1

4/23

Reusability of Classes

Java allows reusability of classes.

Classes created for one program can be

reused for another.

It saves the development time.

It is possible to use classes across

packages even if the classes share thesame name.

You will be able to distinguish the classeswith the help of the package name

7/30/2019 Package Part 1

5/23

Packages

Is a collection of classes that can be shared

by Java programs.

Are classified into

in-built packages

user-defined packages.

7/30/2019 Package Part 1

6/23

Packages

In-built packages User defined packages

Packages

7/30/2019 Package Part 1

7/23

Packages

In-built packages - system packages.

User-defined packages - Created by the

users for their requirements.

7/30/2019 Package Part 1

8/23

Advantages - Packages

Allows reusability across programs.

Allow classes to organize into units.

Used to identify the classes.

Same class name can be used in different

packages.

7/30/2019 Package Part 1

9/23

Java Packages

The classes are grouped together based on

their functionality.

Some of the important packages of Java are: lang

util

Io

awt net

applet.

7/30/2019 Package Part 1

10/23

Important Java Packages

7/30/2019 Package Part 1

11/23

Important Java Packages - Description

PackageName

Description

lang Provides language support classes.

util Provides language utility classessuch as vectors, hash tables random

numbers and date.

io Provides input and output supportclasses.

Cont

7/30/2019 Package Part 1

12/23

Important Java Packages - Description

PackageName

Description

awt Provides set of classes such asbuttons, lists, menus, windows forimplementing graphical interface

net Provides classes for networking.Enables communication between thelocal computers and internet servers

applet Provides classes for creating andimplementing applets

7/30/2019 Package Part 1

13/23

Classes Within Packages

A file name in java has the same name as the

class in which main method is defined.

All the files for the classes within a packagehave to be saved in a directory with the same

name as that of the package.

7/30/2019 Package Part 1

14/23

Structure of io Package

Package

Class

7/30/2019 Package Part 1

15/23

The importStatement

To access the classes from a package, the

importstatement is used.

There are two ways to import packages.

Import all the classes of the package using *.

Import single class using the class name.

7/30/2019 Package Part 1

16/23

Importing all classes

To import all the classes of a package * is

used.Example

import java.io.*;

Syntaximport java.packagename.*;

7/30/2019 Package Part 1

17/23

Importing specific class

To import a specific class, the class name

Example

import java.io.BufferedReader;

Syntax

import java.packagename.classname;

7/30/2019 Package Part 1

18/23

Hands-On!

ProgramInputSample.java accepts inputusing input stream.

7/30/2019 Package Part 1

19/23

Activity 6.9.1

Step 1: OpenInputSample1.java from Student data

file.

Step 2: Type import java.io.*; in Code line 1.

Step 3: Save and Compile the program.

Step 4: Run and observe the output.

7/30/2019 Package Part 1

20/23

Summary

In this presentation, you learnt the following

Package is a collection of classes that can

be shared by Java programs.

Packages provides reusability, they allowclasses to be organized into units. They are

used to identify the classes. Packages enable classes to have same

name across them.

7/30/2019 Package Part 1

21/23

Summary

In this presentation, you also learnt the following

The classes are grouped together based on their

functionality.

Some of the important java packages are lang,

util, io, awt, net and applet. importstatement is used to access the classes

from the packages.

7/30/2019 Package Part 1

22/23

Assignment

1. List the advantages of package.

2. What are the two types of packages?

3. List some of the in-built java packages.

7/30/2019 Package Part 1

23/23

Lab Exercise

1. Write a program to accept a string by

importing the io package.