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Example 1: Displaying multiple strings: Using paint ( ) method
import javax.swing.JApplet; // import class JApplet
import java.awt.Graphics; // import class Graphics
public class WelcomeApplet2 extends JApplet
{
public void paint( Graphics g )
{
g.drawString( "Welcome to", 25, 25 );
g.drawString( "Java Programming!", 25, 40 );
}
}
import java.applet.*;
import java.awt.*;
public
class DrawingLines extends
Applet
{
int
width,
height;
public
void
init()
{
width
= getSize().width;
height
= getSize().height;
setBackground(
Color.black
);
}
public
void
paint( Graphics g )
{
g.setColor(
Color.green
);
for
( int
i = 0; i < 10; ++i )
{
g.drawLine(
width,
height,
i * width
/ 10, 0 );
}
}
}
Example 3: Calculations using init ( ) method
import java.awt.Graphics;
import javax.swing.*;
public class AdditionApplet extends JApplet
{
double sum;
// initialize applet by obtaining values from user
public void init()
{
String firstNumber; // first string entered by user
String secondNumber; // second string entered by user
double number1; // first number to add
double number2; // second number to add
// obtain first number from user
firstNumber = JOptionPane.showInputDialog("Enter first floating-point value" );
// obtain second number from user
secondNumber = JOptionPane.showInputDialog("Enter second floating-point value" );
// convert numbers from type String to type double
number1 = Double.parseDouble( firstNumber );
number2 = Double.parseDouble( secondNumber );
// add numbers
sum = number1 + number2;
}
// draw results in a rectangle on applet’s background
public void paint( Graphics g )
{
// call inherited version of method paint
super.paint( g );
// draw rectangle starting from (15, 10) that is 270
// pixels wide and 20 pixels tall
g.drawRect( 15, 10, 270, 20 );
// draw results as a String at (25, 25)
g.drawString( "The sum is " + sum, 25, 25 );
} // end method paint
} // end class AdditionApplet
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Example 4: Calling methods
import java.awt.Container;
import javax.swing.*;
public class SquareIntegers extends JApplet
{
// set up GUI and calculate squares of integers from 1 to 10
public void init()
{
// JTextArea to display results
JTextArea outputArea = new JTextArea();
// get applet's content pane (GUI component display area)
Container container = getContentPane();
// attach outputArea to container
container.add( outputArea );
int result;
String output = "";
// loop 10 times
for ( int counter = 1; counter <= 10; counter++ )
{
// calculate square of counter and store in result
result = square( counter );
// append result to String output
output += "The square of " + counter + " is " + result + "\n";
}
outputArea.setText( output ); // place results in JTextArea
}
// square method definition
public int square( int y )
{
return y * y;
}
}
Example 5: do while control structure
import java.awt.Graphics;
import javax.swing.JApplet;
public class DoWhileTest extends JApplet
{
// draw lines on applet
public void paint( Graphics g )
{
super.paint( g ); // call paint method inherited from JApplet
int counter = 1; // initialize counter
do
{
g.drawOval( 110 - counter * 10, 110 - counter * 10,
counter * 20, counter * 20 );
++counter;
} while ( counter <= 10 ); // end do...while
} // end method paint
} // end class DoWhileTest
Example 6: switch control structure
import java.awt.Graphics;
import javax.swing.*;
public class SwitchTest extends JApplet
{
int choice;
public void init()
{
String input;
input = JOptionPane.showInputDialog(
"Enter 1 to draw lines\n" +
"Enter 2 to draw rectangles\n" +
"Enter 3 to draw ovals\n" );
choice = Integer.parseInt( input );
}
public void paint( Graphics g )
{
for ( int i = 0; i < 10; i++ )
{
switch( choice ) {
case 1:
g.drawLine( 10, 10, 250, 10 + i * 10 );
break;
case 2:
g.drawRect( 10 + i * 10, 10 + i * 10,
50 + i * 10, 50 + i * 10 );
break;
case 3:
g.drawOval( 10 + i * 10, 10 + i * 10,
50 + i * 10, 50 + i * 10 );
break;
default:
JOptionPane.showMessageDialog(
null, "Invalid value entered" );
} // end switch
} // end for
} // end paint()
} // end class SwitchTest
// Finding the maximum of three floating-point numbers.
import java.awt.Container;
import javax.swing.*;
public class MaximumTest extends JApplet
{
// initialize applet by obtaining user input and creating GUI
public void init()
{
// obtain user input
String s1 = JOptionPane.showInputDialog("Enter first floating-point value" );
String s2 = JOptionPane.showInputDialog("Enter second floating-point value" );
String s3 = JOptionPane.showInputDialog("Enter third floating-point value" );
// convert user input to double values
double number1 = Double.parseDouble( s1 );
double number2 = Double.parseDouble( s2 );
double number3 = Double.parseDouble( s3 );
double max = maximum( number1, number2, number3 ); // method call
// create JTextArea to display results
JTextArea outputArea = new JTextArea();
// display numbers and maximum value
outputArea.setText( "number1: " + number1 + "\nnumber2: " +
number2 + "\nnumber3: " + number3 + "\nmaximum is: " + max );
// get applet's GUI component display area
Container container = getContentPane();
// attach outputArea to Container c
container.add( outputArea );
} // end method init
// maximum method uses Math class method max to help
// determine maximum value
public double maximum( double x, double y, double z )
{
return Math.max( x, Math.max( y, z ) );
} // end method maximum
} // end class Maximum
