Laboratory 14
Lesson 14-2
Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5
Exercise 6
Lesson 14-3
Exercise 1
Exercise 2
Exercise 3
Lesson 14-4
Exercise 1
Exercise 2
Exercise 3
Solutions
Lesson 14-2
Exercise 1:
The following is an example of the class heading and shell for the applet OddEven.
import java.awt.*;
// Supplies layout manager
import java.awt.event.*; // Supplies event classes
import javax.swing.*;
// Supplies class JApplet and GUI components
public class OddEvenApplet extends JApplet implements ActionListener
{
// Declaring fields
/* TO BE FILLED IN: Exercise 3 */
// Event handler method
public void actionPerformed(ActionEvent event)
{
/* TO BE FILLED IN: Exercise 2 */
}
public void init()
{
/* TO BE FILLED IN: Exercise 4 */
}
}
Exercise 2:
The following is an example of the actionPerformed method.
// Event handler method
public void actionPerformed(ActionEvent event)
{
int number = 0;
try
{
number = Integer.parseInt(inputField.getText());
if ( Math.abs(number) < 100 || Math.abs(number) > 999 )
throw new NumberFormatException();
}
catch( NumberFormatException e ) {
JOptionPane.showMessageDialog( this,
"Please enter a three digit integer.",
"Error: Wrong input!", JOptionPane.ERROR_MESSAGE );
return;
}
if ((number / 2) * 2 == number)
outLabelUnits.setText("Unit's position is even.");
else
outLabelUnits.setText("Unit's position is odd.");
if ((((number / 10) / 2) * 2) == (number / 10))
outLabelTens.setText("Ten's position is even.");
else
outLabelTens.setText("Ten's position is odd.");
if ((((number / 100) / 2) * 2) == (number / 100))
outLabelHundreds.setText("Hundred's position is even.");
else
outLabelHundreds.setText("Hundred's position is odd.");
}
Exercise 3:
The following are the variables that are needed for this applet.
// Declaring fields
private JTextField inputField;
private JButton button;
private JLabel outLabelUnits, outLabelTens, outLabelHundreds;
Exercise 4:
The following is an example of the init method.
public void init()
{
// Set layout for GUI components
setLayout(new GridLayout(6,0));
// Instantiate GUI components
JLabel label;
label =
new JLabel("Enter a three digit number and click enter button");
outLabelUnits = new JLabel("Units");
outLabelTens = new JLabel("Tens");
outLabelHundreds = new JLabel("Hundreds");
button = new JButton("enter");
button.addActionListener(this);
inputField = new JTextField("Value here");
// Add window compontents
add(label);
add(inputField);
add(button);
add(outLabelHundreds);
add(outLabelTens);
add(outLabelUnits);
}
Exercise 5:
The following is an example of the complete applet.
import java.awt.*;
// Supplies layout manager
import java.awt.event.*; // Supplies event classes
import javax.swing.*;
// Supplies class JApplet and GUI components
public class OddEvenApplet extends JApplet implements ActionListener
{
// Declaring fields
private JTextField inputField;
private JButton button;
private JLabel outLabelUnits, outLabelTens, outLabelHundreds;
// Event handler method
public void actionPerformed(ActionEvent event)
{
int number = 0;
try
{
number = Integer.parseInt(inputField.getText());
if ( Math.abs(number) < 100 || Math.abs(number) > 999 )
throw new NumberFormatException();
}
catch( NumberFormatException e ) {
JOptionPane.showMessageDialog( this,
"Please enter a three digit integer.",
"Error: Wrong input!", JOptionPane.ERROR_MESSAGE );
return;
}
if ((number / 2) * 2 == number)
outLabelUnits.setText("Unit's position is even.");
else
outLabelUnits.setText("Unit's position is odd.");
if ((((number / 10) / 2) * 2) == (number / 10))
outLabelTens.setText("Ten's position is even.");
else
outLabelTens.setText("Ten's position is odd.");
if ((((number / 100) / 2) * 2) == (number / 100))
outLabelHundreds.setText("Hundred's position is even.");
else
outLabelHundreds.setText("Hundred's position is odd.");
}
public void init()
{
// Set layout for GUI components
setLayout(new GridLayout(6,0));
// Instantiate GUI components
JLabel label;
label =
new JLabel("Enter a three digit number and click enter button");
outLabelUnits = new JLabel("Units");
outLabelTens = new JLabel("Tens");
outLabelHundreds = new JLabel("Hundreds");
button = new JButton("enter");
button.addActionListener(this);
inputField = new JTextField("Value here");
// Add window compontents
add(label);
add(inputField);
add(button);
add(outLabelHundreds);
add(outLabelTens);
add(outLabelUnits);
}
}
The following HTML code runs the IntegerRead applet.
<applet code="OddEvenApplet.class" width=400 height=200></applet>
Exercise 6:
The OddEven applet inputs a three digit integer, and determines whether each digit is
odd/even. Test the applet with a sufficient number of (positive/negative) integer inputs to
cover all possible combinations of odd/even. For example:
Three Digit Input Integer
Hundreds
Tens
Units
Even
Even
Even
Odd
Odd
Odd
Even
Odd
Odd
Even
Odd
Odd
Even
Even
Odd
Even
Even
Odd
Also, test the applet with some invalid inputs, such as integers with less/more than three
digits, floating point numbers, and nonnumeric characters.
The following are the results.
Input
444
632
815
-928
-714
931
0
23
-1001
1.2
-3.45
Enter nothing;
just press Enter.
Expected Results
Hundred’s position is even.
Ten’s position is even.
Unit’s position is even.
Hundred’s position is even.
Ten’s position is odd.
Unit’s position is even.
Hundred’s position is even.
Ten’s position is odd.
Unit’s position is odd.
Hundred’s position is odd.
Ten’s position is even.
Unit’s position is even.
Hundred’s position is odd.
Ten’s position is odd.
Unit’s position is even.
Hundred’s position is odd.
Ten’s position is odd.
Unit’s position is odd.
Error: Wrong input!
Please enter a three digit
integer.
Error: Wrong input!
Please enter a three digit
integer.
Error: Wrong input!
Please enter a three digit
integer.
Error: Wrong input!
Please enter a three digit
integer.
Error: Wrong input!
Please enter a three digit
integer.
Error: Wrong input!
Please enter a three digit
integer.
Actual Results
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
As expected.
XY
Error: Wrong input!
Please enter a three digit
integer.
As expected.
Lesson 14-3
Exercise 1:
The following is an example of the applet.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
// Supplies layout manager
// Supplies event classes
// Supplies class Applet
public class IntegerRead extends JApplet implements ActionListener
{
// Declaring fields
private JTextField inputField;
private JButton button;
private JLabel outLabel;
// Event handler method
public void actionPerformed(ActionEvent event)
{
String input = inputField.getText();
try
{
int num = Integer.parseInt( input );
if ( num < 0 )
input = Integer.toString( Math.abs( num ) );
}
catch( NumberFormatException e ) {
JOptionPane.showMessageDialog( this,
"Please enter a valid integer.",
"Error: Wrong input!", JOptionPane.ERROR_MESSAGE );
return;
}
if (input.length()/2 * 2 == input.length())
outLabel.setText("The integer has an even number of digits");
else
outLabel.setText("The integer has an odd number of digits");
}
public void init()
{
setLayout(new GridLayout(4,0));
JLabel label =
new JLabel("Enter an integer and click enter button");
outLabel = new JLabel("odd or even?");
button = new JButton("enter");
button.addActionListener(this);
inputField = new JTextField("Value here");
// Add window compontents
add(label);
add(inputField);
add(button);
add(outLabel);
}
}
The test cases include:
A valid integer with an odd number of digits: 123
A valid integer with an even number of digits: -4567
An invalid number: 123.45
An invalid number: qwer5
An empty string (just clicking Enter)
Exercise 2:
The following is an example of the applet.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
// Supplies layout manager
// Supplies event classes
// Supplies class Applet
public class StringReverse extends JApplet implements ActionListener
{
// Declaring fields
private JTextField inputField;
private JButton button;
private JLabel outLabel;
// Event handler method
public void actionPerformed(ActionEvent event)
{
String input;
String reverseInput;
input = inputField.getText();
// Input String must have at least one (visible) character
try
{
// Remove leading and trailing spaces
String temp = input.trim();
// If String length is 0, throw an exception
if ( temp.length() < 1 )
throw new Exception();
}
catch( Exception e ) {
JOptionPane.showMessageDialog( this,
"Input String must have at least one (visible) character.",
"Error: Wrong input!", JOptionPane.ERROR_MESSAGE );
return;
}
char[] inputChar = input.toCharArray();
char[] inputCharReverse = new char [inputChar.length];
// Reverse String
for (int position = inputChar.length-1; position >= 0; position--)
inputCharReverse[inputChar.length-1-position] =
inputChar[position];
reverseInput = String.valueOf(inputCharReverse);
outLabel.setText("Reversed String is : " + reverseInput);
inputField.setText("");
}
public void init()
{
setLayout(new GridLayout(4,0));
JLabel label = new JLabel("Enter a string and click enter button");
outLabel = new JLabel("Reverse order string is");
button = new JButton("Enter");
button.addActionListener(this);
inputField = new JTextField("String here");
// Add window compontents
add(label);
add(inputField);
add(button);
add(outLabel);
}
}
Exercise 3:
The following is an example of the applet.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
// Supplies layout manager
// Supplies event classes
// Supplies class Applet
public class DateFormat extends JApplet implements ActionListener
{
// Declaring fields
private JTextField inputDay;
private JTextField inputMonth;
private JTextField inputYear;
private JButton button;
private JLabel outLabelUS, outLabelEng;
// Event handler method
public void actionPerformed(ActionEvent event)
{
String day = inputDay.getText();
String month = inputMonth.getText();
String year = inputYear.getText();
outLabelUS.setText("US: " + month + " " + day + " " + year);
outLabelEng.setText("English: " + day + " " + month + " " + year);
inputDay.setText("");
inputMonth.setText("");
inputYear.setText("");
}
public void init()
{
setLayout(new GridLayout(5,2));
JLabel label, labelDay, labelMonth, labelYear;
label = new JLabel("");
labelDay = new JLabel("Enter the day");
labelMonth = new JLabel("Enter the month");
labelYear = new JLabel("Enter a year and click enter button");
outLabelUS = new JLabel("US date format");
outLabelEng = new JLabel("English date format");
button = new JButton("enter");
button.addActionListener(this);
inputDay
= new JTextField("Day here");
inputMonth = new JTextField("Month here");
inputYear = new JTextField("Year here");
// Add window compontents
add(label);
add(button);
add(labelDay);
add(inputDay);
add(labelMonth);
add(inputMonth);
add(labelYear);
add(inputYear);
add(outLabelUS);
add(outLabelEng);
}
}
Lesson 14-4
Exercise 1:
The following code runs the IntegerRead applet.
<applet code="IntegerRead.class" width=400 height=200></applet>
Exercise 2:
The following code runs the StringReverse applet.
<applet code="StringReverse.class" width=400 height=200></applet>
Exercise 3:
The following code runs the DateFormat applet.
<applet code="DateFormat.class" width=400 height=200></applet>