1. GUI Graphical User Interface Each onscreen component and window is an object Object interaction makes communication and scoping challenging Event-driven - program’s execution is driven by the series of events that occur

2. Option pane – simple message box Includes a message or request for input JOptionPane

3. Parsing Number Strings Integer.parseInt(strExpression) Float.parseFloat(strExpression) Double.parseDouble(strExpression) Examples: Integer.parseInt(“-542”) = -542 Float.parseFloat(“34.63”) = 34.63 Double.parseDouble(“-758.873”) = -758.873

4. Integer, Float, Double Classes Convert string to a number Wrapper classes parseInt is a method of class Integer parseFloat…

5. Using Dialog boxes GUI Class JOptionPane Contained in package javax.swing In earlier versions of java, Swing was an extension to Java’s feature set Two methods: – To present a list of choices to the user showInputDialog – Display a message showMessageDialog (parent window, display string) import javax.swing.*;

6. Gui1 import javax.swing.*; // for GUI components public class Gui1 { public static void main(String [] args) { JOptionPane.showMessageDialog(null, "Hello world!"); }

7. JOptionPane 1.Display a message (showMessageDialog) 2.To present a list of choices to the user (showInputDialog) 3.To ask the user to type input (showConfirmDialog)

8. GUI2 import javax.swing.*; // for GUI components public class Gui2 { public static void main(String [] args) { String name = JOptionPane.showInputDialog(null, "What is your name"); int choice = JOptionPane.showConfirmDialog(null, "Do you like chocolate, " + name + "?"); if (choice == JOptionPane.YES_OPTION) { JOptionPane.showMessageDialog(null, "Of course! Who doesn't?"); } else JOptionPane.showMessageDialog(null, "Seriously?"); }

9. showMessageDialog JOptionPane.showMessageDialog(parentComponent, messageStrExp, boxTitleStr, messageType); parentComponent – null causes dialog box to appear in middle of string messageStrExp – appears in dialog box boxTitleString – title of dialog box messageType – ERROR_MESSAGE – error icon INFORMATION_MESSAGE – information icon PLAIN_MESSAGE – no icon QUESTION_MESSAGE – question icon WARNING_MESSAGE – warning icon

10. import javax.swing.*; public class AreaAndCircumferenceProgram { public static final double PI = 3.14; public static void main(String[] args) { double radius, area, circumference; String radiusString,outputStr; radiusString = JOptionPane.showInputDialog(“Enter radius:"); radius = Double.parseDouble(radiusString); area = PI * radius * radius; circumference = 2 * PI * radius; outputStr = "Radius: " + radius + "\nArea: " + area + " square units\n" + "Circumference: " + circumference + " units"; JOptionPane.showMessageDialog(null, outputStr, "Circle", JOptionPane.INFORMATION_MESSAGE); System.exit(0); }

11. String method format String.format(formatString,argumentList) Works like printf Can be used as argument to println Double x = 15.674; Double y = 235.73; Double z = 9525.9864; System.out.println(String.format(“%.2f”,x); System.out.println(String.format(“%.3f”,y); System.out.println(String.format(%.2f”,z);

12. import javax.swing.*; public class AreaAndCircumferenceProgram { public static final double PI = 3.14; public static void main(String[] args) { double radius, area, circumference; String radiusString,outputStr; radiusString = JOptionPane.showInputDialog(“Enter radius"); radius = Double.parseDouble(radiusString); area = PI * radius * radius; circumference = 2 * PI * radius; outputStr = String.format("Radius: %.2f %n Area: %.2f square units %nCircumference: %.2f units", radius, area, circumference); JOptionPane.showMessageDialog(null, outputStr, "Circle", JOptionPane.INFORMATION_MESSAGE); }

13. str = JOptionPane.showInputDialog(stringExpr); radiusStr = JOptionPane.showInputDialog(“Enter the radius:”)