Unit 5 Java Programming with Linux-converted.pdf

Contents
• Applet Fundamentals
• Applet Tag
• Applet life-cycle
• Passing parameters to applets
• Graphics Programming
• JDBC drivers
• JDBC connection
2 September 2021 2

Applets
• Small Java programs that can be downloaded and
executed in a Java enabled Web browser.
• Transported via internet.
• Perform arithmetic operations, display graphics,
play sounds, create animations, play interactive
games etc.
• Two types of applets
1. Local applet
2. Remote applet
2 September 2021 3

Applets
• Applet developed locally and stored in a local
system is known as local applet.
• Does not require any internet connection.
• Remote applet is developed by someone else
and stored on a remote computer.
• If our computer is connected to internet, we
can download a remote applet via internet
and runs it.
2 September 2021 4

Building applet code
• Two classes Applet and Graphics needs to be
imported.
• The Applet class is contained in the java.applet
package.
Example Program
2 September 2021 5

Applet Tag
• <applet> tag is used to start an applet from an HTML
document and from an appletviewer.
<Applet>
[CODE BASE=codebase URL]
CODE = appletfile
[ALT=alternate Text]
WIDTH=pixels HEIGHT=pixels
[ALIGN=alignment]
[<PARAM NAME=attributename1 VALUE=value1>]
</Applet>
2 September 2021 6

Applet Tag
[CODE BASE=codebase URL] – This is an optional
attribute which specifies the directory that
will be searched for the applet’s executable
class file.
CODE = appletfile – This is a required attribute
that gives the name of the file that contains
the applet compiled subclass.
2 September 2021 7

Applet Tag
[ALT=alternate Text] – This is an optional
attribute which specifies a short text message
that should be displayed if the browser
understands the applet tag, but cannot run
Java applets.
WIDTH=pixels HEIGHT=pixels – These are
required attributes that give the initial size in
pixels of the applet display area.
2 September 2021 8

Applet Tag
[ALIGN=alignment] - This is an optional
attribute that specifies the alignment of the
attribute.
[<PARAM NAME=attributename1
VALUE=value1>] – This attribute is used to
pass parameter to applets.
2 September 2021 9

Passing Parameters to Applets
• Each <PARAM> tab has a NAME attribute and a
VALUE attribute.
• Example
<Applet>
<PARAM NAME=COLOR VALUE=“Red”>
</Applet>
Example Program
2 September 2021 10

Life Cycle of an Applet
2 September 2021 11

2 September 2021 12
• init() – this method is called first. This is where
we should initialize variables.
• start() – this method is called after init(). This
is also called after an applet has been
stopped. While init() is called once(first time
an applet is loaded), start() is called each time
an applet’s HTML document is displayed on
screen. For example, a user leaves a Web page
and comes back.

2 September 2021 13
• paint() – This method is called each time the
applet is damaged. If any other window covers
the applet, the window system calls paint()
method.
• update() – The default update method in class
Applet first fills an applet with default
background color and then calls paint().

2 September 2021 14
• stop() – This method is called when a Web
browser leaves the HTML document containing
the applet. When the user returns to the page
applets are restarted using start() method.
• destroy() – This method is called when the
runtime environment determines that the applet
needs to be removed completely from memory.
• repaint() – Calling repaint() in turn calls update()
method.

2 September 2021 15
• Getting Input from the user – Example
Program

Graphics Programming
• Every applet has its own area of the screen
called canvas.
• Java’s co-ordinate system has the origin(0,0) in
the upper left corner.
• Positive x-values are to the right and positive
y-values are to the bottom.
• The value of co-ordinates x and y are in pixels.
2 September 2021 16

Graphics Class - Methods
1. drawArc() – draws an arc.
2. drawLine() – draws a straight line.
3. drawOval() – draws an oval.
4. drawPolygon() – draws a polygon.
5. drawRect() – draws a hollow rectangle.
6. drawRoundRect() – draws a hollow rectangle
with rounded corners.
2 September 2021 17

7. drawString() – displays a string.
8. fillArc() – draws a filled arc.
9. fillOval() – draws a filled oval.
10. fillPolygon() – draws a filled polygon.
11.fillRect() – draws a filled rectangle.
12.fillRoundRect() – draws a filled rectangle with
rounded corners.
13.getColor() – retrieves the current drawing color.
14.setColor() – sets the drawing color.
2 September 2021 18

Example program for drawLine(), drawRect(),
fillRect(),drawRoundRect(), fillRoundRect()
• drawLine() method takes 2 pairs of co-
ordinates and draws a line between them.
• drawRect() method takes 4 arguments, first
two represents the x and y co-ordinates of
the top left corner of the rectangle and
remaining 2 represents the width and height
of the rectangle.
2 September 2021 19

• fillRect() method is similar to drawRect()
except that it draws a solid rectangle.
• fillRoundRect() and drawRoundRect() method
takes 6 arguments, the two extra arguments
representing the width and height of the
angle of corners.
2 September 2021 20

Example Program for drawOval()
• drawOval() method can be used to draw a
circle.
• Takes 4 arguments. The first 2 represent the
top left corner of the imaginary rectangle and
the other 2 represents the width and height
of the oval itself.
• If the width and height are same, the oval
becomes a circle.
2 September 2021 21

Example Program for drawArc() and fillArc()
• drawArc() and fillArc() method takes 6
arguments. The first 4 is same as that of
drawOval(), and the last 2 represent the start
angle and sweep angle (no: of degrees)
around the arc.
• Zero degrees is at 3’O Clock and degrees
increase in a counter-clockwise direction.
2 September 2021 22

Example Program for drawPolygon() and
fillPolygon()
• Both have the form drawPolygon(int[],
int[],int) and fillPolygon(int[], int[], int).
2 September 2021 23

Color Class
• We can use static variables in Color to specify
a number of common colors. (Example:
Color.blue)
• Color(int,int,int) – takes red green and blue
integers between 0 and 255.
• Color(float,float,float) – takes 3 float values
between 0.0 and 1.0 for red, green and blue.
2 September 2021 24

Java Data Base Connectivity-JDBC
2 September 2021 25
4 Types of JDBC Drivers
1. JDBC-ODBC bridge driver
2. Native-API driver (partially Java driver)
3. Network Protocol driver (fully Java driver)
4. Thin driver (fully Java driver)

JDBC-ODBC bridge driver
2 September 2021 26

Native-API driver (partially Java driver)
2 September 2021 27

Network Protocol driver (fully Java
driver)
2 September 2021 28

Thin driver (fully Java driver)
2 September 2021 29

Steps to connect to a Database
1. Register the driver class.
2. Create the connection object.
3. Create the Statement object.
4. Execute the query.
5. Close the connection object
2 September 2021 30

1. Register the driver class
• The forName() method of Class is used to
register the driver class.
• This method is used to dynamically load the
driver class.
• Syntax of forName() method
Class.forName(“com.mysql.jdbc.Driver")
2 September 2021 31

2. Create the connection object
• getConnection() method of DriverManager
class is used to establish connection with the
database.
• Syntax of getConnection() method.
Connection conn = DriverManager.getConnection(dbURL,
username, password);
Example
Connection con=DriverManager.getConnection(
"jdbc:mysql://localhost3306/mysql",“root","");
2 September 2021 32

3. Create the Statement object
• createStatement() method of Connection
interface is used to create statement.
• Example of createStatement() method.
Statement stmt=con.createStatement();
2 September 2021 33

4. Execute the query
• The executeQuery() method of Statement interface is
used to execute queries to the database.
• This method returns the object of ResultSet that can
be used to get all the records of a table.
Example
ResultSet rs=stmt.executeQuery("select * from emp");
while(rs.next()){
System.out.println(rs.getInt(1)+" "+rs.getString(2));
}
2 September 2021 34

5 Close the connection object
• By closing connection object statement and
ResultSet will be closed automatically.
• The close() method of Connection interface is
used to close the connection.
Example
con.close();
2 September 2021 35

DriverManager Class
• DriverManager class acts as an interface
between user and drivers.
• It keeps track of the drivers that are available
and handles establishing a connection
between a database and the appropriate
driver.
2 September 2021

DriverManager Class - Methods
• public static void registerDriver(Driver driver): To
register the given driver with DriverManager.
• public static void deregisterDriver(Driver driver):To
deregister the given driver with DriverManager.
• public static Connection getConnection(String url):To
establish the connection with the specified url.
• public static Connection getConnection(String url,String
userName,String password): To establish the
connection with the specified url, username and
password.
2 September 2021

Connection Interface
• Provides many methods for transaction
management like commit(), rollback() etc.
• By default, connection commits the changes
after executing queries.
2 September 2021

Connection Interface - Methods
• public Statement createStatement(): creates a
statement object that can be used to execute SQL
queries.
• public void setAutoCommit(boolean status): is used to
set the commit status. By default it is true.
• public void commit(): saves the changes made since
the previous commit/rollback permanent.
• public void rollback(): Drops all changes made since the
previous commit/rollback.
• public void close(): closes the connection and releases
a JDBC resource immediately.
2 September 2021

Statement Interface - Methods
• Provides methods to execute queries with the
database.
• public ResultSet executeQuery(String sql): is
used to execute SELECT query. It returns the
object of ResultSet.
• public int executeUpdate(String sql): is used to
execute specified query. It may be create,
drop, insert, update, delete etc.
2 September 2021

Programs
• Insert Records
• Update Records
• Delete Records
2 September 2021 41

End of Unit 5
2 September 2021 42

Unit 5 Java Programming with Linux-converted.pdf

More Related Content

Similar to Unit 5 Java Programming with Linux-converted.pdf

Recently uploaded

Unit 5 Java Programming with Linux-converted.pdf