1. Advanced Java Programming CSE 7345/5345/ NTU 531
Welcome Back!!!
Advanced Java Programming CSE 7345/5345/ NTU 531
Session 7

2. Chantale Laurent-Rice
Office Hours:
by appt
3:30pm-4:30pm
SIC 353
Chantale Laurent-Rice
Welcome Back!!!

3. Short review Packages
In Java, each class is defined in a single file called ClassName.java.
A package is a name for a set of related classes,
Java uses package names to locate classes at compile-time and at runtime.
Packages can be seen as some kind of libraries in which the classes are grouped.
The difference is that packages provide an additional scope.
Each class file must belong to a package:
Example:
Package dpack;
Package java.awt.event;

4. Packages con’t
If no package is given, the class is placed in a default package with no name.
A compilation unit (a file) declares one or more classes. It is a file that may contain several class declarations. It is used as an input for the java Compiler (javac) which outputs a series of class files (bytecodes).
There is a class file for each class in the compilation unit.
At the most one class is declared public.
Example:
Source code: ClassName.java hello.java
Bytecode: className.class hello.class

5. Packages con’t
To use the classes, one or more modules in a program can import the entire package with the declaration, such as
import graphics.*;
The asterisk indicates to the compiler that it should import all classes in the graphics package.

6. Standard packages Java.applet- provides the means to create applet
Java.awt provides class-based GUI with windows
Java.awt.*- have subpackages such as java.awt,color, java.awt.font, and java.awt.image
Java.beans- provides basic elements for JavaBeans
Java.io provides I/O
Java.lang- wrapper classes such as: Char, int, Double, String and StringBuffer
java.math- math programmers
Java.net- network, socket handler, internet utility classes
Java.rmi- Remote Method Invocation provide support for distributed code controlled by remote interface
Java.security- implements security, encryption keys, and certificates
Java.sql implements of Structured Query Language database fields types and methods
Java.text- provide parsers and formatters
Java.util- Java Application and applet (Random class, Collection, list, Set) packages container class.
Java.util.jar- subpackage w/I java.util.
Java.util.zip- subpackage for .zip file compression format.

7. Packages con’t To import just one class: import graphics.Rectangle;
It is not correct to import the package itself:
import graphics;
Some packages provide one or more subpackages, such as java.util.jar, a subpackage of java.util.
Importing a package does not import any subpackages.
You must do that explicitly using statements like these:
Import java.utils.*;
Import java.utils.jar.*;

8. Small Quiz
What happen if you tried to compile and run the following code?
public class EqualsTest{
public static void main(String[] args){
Long L = new Long( 7 );
4. if( L.equals( 7L))
5. System.out.println(“Equal”);
else System.out.println(“Not Equal”);
6. }
7. }
The program would compile and print “Equal”
The program would compile and print “Not Equal”.
The compiler would object to line 4.
A runtime cast error would occur at line 4.

9. Small Quiz C. qualsTest.java:5: cannot resolve symbol
symbol : method equals (long)
location: class java.lang.Long
if( L.equals( 7L)) ^
1 error
The compiler knows that the equals method takes an Object rather than a primitive as input. Because the compiler does not compile answer a, b, d are incorrect.

10. Small Quiz
What happen if you tried to compile and run the following code?
public class EqualsTest{
public static void main(String[] args){
Object A = new Long ( 7 );
Long L = new Long( 7 );
5. if( A.equals( L ))
System.out.println(“Equal”);
6. else System.out.println(“Not Equal”);
7. }
8. }
The program would compile and print “Equal”
The program would compile and print “Not Equal”.
The compiler would object to line 5.
A runtime cast error would occur at line 5.

11. Small Quiz a.
Because the Long object created in line 3 does not lose its identity when cast to Object A, so the equals method knows the class is correct and compares the values.
Answer c, d, do not occur because this is the correct form for comparing objects with the equals method. Therefore, they are incorrect.

12. What compile-time error is generated for the following program?
interface
What compile-time error is generated for the following program?
interface B{
void display(); }
class D1{
class D2 implements B{
public void display() {
System.out.println("D2");
class D3 implements B {
public void display() {
System.out.println("D3"); }
class InterfaceRefVar{
public static void main(String[] args){
B b;
b = new D1();
b.display();
b = new D2();
b = new D3();

13. interface
The line “b = new D1();” generates an error because the types are incompatible for assignment. Class D1 does not implements interface B.
C:\InterfaceRefVar.java:23: incompatible types
found : D1
required: B
b = new D1(); ^
1 error

14. Chapter 10 Getting Started with GUI Programming
GUI Class Hierarchy
Frames
Creating frames, centering frames, adding components to frames
Layout Managers
FlowLayout, GridLayout, BorderLayout
Drawing on Panels
The paintComponent method
Using Colors, Fonts, and Font Metrics
Drawing Geometric Figures
Lines, Rectangles, Ovals, Arcs, and Polygons
Event-Driven Programming
Event Source, Listener, Listener Interface

15. AWT/JFC
AWT was a powerful toolkit when introduced
it was the original driving force behind Java’s popularity
is today’s standard , a limited implementation
not designed to provide a serious, main UI for the needs of many programmers.
Now Swing, which has about four times the number of user interface (UI) components as the AWT
Swing is part of the standard Java distribution

16. AWT (Optional)

17. Question?
Is JFC and Swing the same?

18. JFC
Many programmer that that JFC and Swing are the same thing, but that’s not so; the JFC contains Swing and quite a number of other items.

19. What’s in JFC? Swing- The large UI package
Cut and paste- Clipboard support
Accessibility features- Aimed at users with disabilities.
The desktop Colors features- First introduced in Java 1.1
Java2D- Improved color, image, and text support
Printing- Originally enabled in Java 1.1

20. What’s in Swing? Class Description
AbstractButton Abstract superclass for Swing buttons
ButtonGroup Encapsulates a mutually exclusive set of buttons
ImageIcon Encapsulates an icon
JApplet The Swing version of Applet
JButton The Swing push button class
JCheckBox The Swing check box class
JComboBox Encapsulates a combo box
JLabel The Swing version of a label
JRadioButton The Swing version of a radio button
JScrollPane Encapsulates a scrollable window
JTable Encapsulates a table-based control
JTextField The Swing version of a text field
JTree Encapsulates a tree-based control

21. GUI Class Hierarchy (Swing)

22. JComponent

23. JApplets
Fundamental to Swing is the JApplet class, which extends Applet.
Applets that use Swing must be subclasses of JApplet.
JApplet is rich with functionality that is not found in Applet.
For Example:
JApplet support various “panes”, such as the content pane, the glass pane, and the root pane.

24. Frames
Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications.
The Frame class can be used to create windows.
For Swing GUI programs, use JFrame class to create widows.

25. UI Components

26. Creating Frames import javax.swing.*; public class MyFrame {
public static void main(String[] args) {
JFrame frame = new JFrame("Test Frame");
frame.setSize(400, 300);
frame.setVisible(true);
frame.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE); }
NOTE: You must have JDK 1.3 or higher to run the slides.
Run

27. Centering Frames
By default, a frame is displayed in the upper-left corner of the screen.
To display a frame at a specified location, you can use the setLocation(x, y) method in the JFrame class.
This method places the upper-left corner of a frame at location (x, y).

28. Centering Frames, cont.
Run

29. Adding Components into a Frame
// Add a button into the frame
frame.getContentPane().add(
new JButton("OK"));
Run

30. NOTE
The content pane is a subclass of Container. The statement in the preceding slide can be replaced by the following two lines:
Container container = frame.getContentPane();
container.add(new JButton("OK"));
You may wonder how a Container object is created. It is created when a JFrame object is created. A JFrame object uses the content pane to hold components in the frame.

31. Layout Managers
Java’s layout managers provide a level of abstraction to automatically map your user interface on all window systems.
The UI components are placed in containers. Each container has a layout manager to arrange the UI components within the container.

32. Kinds of Layout Managers
FlowLayout (Chapter 10)
GridLayout (Chapter 10)
BorderLayout (Chapter 10)
CardLayout (Chapter 12)
GridBagLayout (Chapter 12)

33. Example 10.1 Testing the FlowLayout Manager
The components are arranged in the container from left to right in the order in which they were added. When one row becomes filled, a new row is started.
Run

34. FlowLayout Constructors
public FlowLayout(int align, int hGap, int vGap)
Constructs a new FlowLayout with a specified alignment, horizontal gap, and vertical gap. The gaps are the distances in pixel between components.
public FlowLayout(int alignment)
Constructs a new FlowLayout with a specified alignment and a default gap of five pixels for both horizontal and vertical.
public FlowLayout()
Constructs a new FlowLayout with a default center alignment and a default gap of five pixels for both horizontal and vertical.

35. Example 10.2 Testing the GridLayout Manager
The GridLayout manager arranges components in a grid (matrix) formation with the number of rows and columns defined by the constructor. The components are placed in the grid from left to right starting with the first row, then the second, and so on.
Run

36. GridLayout Constructors
public GridLayout(int rows, int columns)
Constructs a new GridLayout with the specified number of rows and columns.
public GridLayout(int rows, int columns, int hGap, int vGap)
Constructs a new GridLayout with the specified number of rows and columns, along with specified horizontal and vertical gaps between components.

37. Example 10.3 Testing the BorderLayout Manager
add(Component, constraint), where constraint is BorderLayout.EAST, BorderLayout.SOUTH, BorderLayout.WEST, BorderLayout.NORTH, or BorderLayout.CENTER.
The BorderLayout manager divides the container into five areas: East, South, West, North, and Center. Components are added to a BorderLayout by using the add method.
Run

38. Example 10.3, cont.
Run

39. Using Panels as Containers
Panels act as smaller containers for grouping user interface components.
It is recommended that you place the user interface components in panels and place the panels in a frame. You can also place panels in a panel.

40. Example 10.4 Testing Panel
This example uses panels to organize components. The program creates a user interface for a Microwave oven.
Run

41. Drawing on Panels
JPanel can be used to draw graphics (including text) and enable user interaction.
To draw in a panel, you create a new class that extends JPanel and override the paintComponent method to tell the panel how to draw things. You can then display strings, draw geometric shapes, and view images on the panel.

42. Drawing on Panels, cont. public class DrawMessage extends JPanel {
/** Main method */
public static void main(String[] args) {
JFrame frame = new JFrame("DrawMessage");
frame.getContentPane().add(new DrawMessage());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(300, 200);
frame.setVisible(true); }
/** Paint the message */
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("Welcome to Java!", 40, 40);

43. Drawing on Panels, cont.

44. NOTE
The Graphics class is an abstract class for displaying figures and images on the screen on different platforms.
The Graphics class is implemented on the native platform in the JVM. When you use the paintComponent method to draw things on a graphics context g, this g is an instance of a concrete subclass of the abstract Graphics class for the specific platform.
The Graphics class encapsulates the platform details and enables you to draw things uniformly without concerning specific platforms.

45. NOTE
Whenever a component is displayed, a Graphics object is created for the component.
The Swing components use the paintComponent method to draw things.
The paintComponent method is automatically invoked to paint the graphics context when the component is first displayed or whenever the component needs to be redisplayed.
Invoking super.paintComponent(g) is necessary to ensure that the viewing area is cleared before a new drawing is displayed.

46. In fact, you can draw things on any GUI component.
NOTE
To draw things, normally you create a subclass of JPanel and override its paintComponent method to tell the system how to draw.
In fact, you can draw things on any GUI component.

47. The Color Class
You can set colors for GUI components by using the java.awt.Color class. Colors are made of red, green, and blue components, each of which is represented by a byte value that describes its intensity, ranging from 0 (darkest shade) to 255 (lightest shade). This is known as the RGB model.
Color c = new Color(r, g, b);
r, g, and b specify a color by its red, green, and blue components.
Example:
Color c = new Color(228, 100, 255);

48. Setting Colors
You can use the following methods to set the component’s background and foreground colors:
setBackground(Color c)
setForeground(Color c)
Example:
setBackground(Color.yellow); setForeground(Color.red);

49. The Font Class Example: Font myFont = Font(name, style, size);
Font myFont = new Font("SansSerif ", Font.BOLD, 16);
Font myFont = new Font("Serif", Font.BOLD+Font.ITALIC, 12);

50. Finding All Available Font Names
GraphicsEnvironment e =
GraphicsEnvironment.getLocalGraphicsEnvironment();
String[] fontnames = e.getAvailableFontFamilyNames();
for (int i = 0; i < fontnames.length; i++)
System.out.println(fontnames[i]);

51. Setting Fonts public void paint(Graphics g) {
Font myFont = new Font("Times", Font.BOLD, 16);
g.setFont(myFont);
g.drawString("Welcome to Java", 20, 40);
//set a new font
g.setFont(new Font("Courier", Font.BOLD+Font.ITALIC, 12));
g.drawString("Welcome to Java", 20, 70); }

52. The FontMetrics Class g.getFontMetrics(Font f); or g.getFontMetrics();
public void paint(Graphics g) {
g.getFontMetrics(Font f); or
g.getFontMetrics(); }

53. Get FontMetrics public int getAscent() public int getDescent()
public int getLeading()
public int getHeight()
public int stringWidth(String str)

54. Example 10.5 Using FontMetrics
Objective: Display “Welcome to Java” in SansSerif 20-point bold, centered in the frame.
Run

56. Example 10.5, cont.

57. Drawing Geometric Figures
Drawing Lines
Drawing Rectangles
Drawing Ovals
Drawing Arcs
Drawing Polygons

58. Drawing Lines
drawLine(x1, y1, x2, y2);

59. Drawing Rectangles
drawRect(x, y, w, h);
fillRect(x, y, w, h);

60. Drawing Rounded Rectangles
drawRoundRect(x, y, w, h, aw, ah);
fillRoundRect(x, y, w, h, aw, ah);

61. Drawing Ovals
drawOval(x, y, w, h);
fillOval(x, y, w, h);

62. Drawing Arcs drawArc(x, y, w, h, angle1, angle2);
fillArc(x, y, w, h, angle1, angle2);

63. Drawing Polygons int[] x = {40, 70, 60, 45, 20};
int[] y = {20, 40, 80, 45, 60};
g.drawPolygon(x, y, x.length);
g.fillPolygon(x, y, x.length);

64. Example 10.6 Drawing a Clock
Objective: Use drawing and trigonometric methods to draw a clock showing the specified hour, minute, and second in a frame.
Run

65. Drawing Clock xEnd = xCenter + handLength  sin()
yEnd = yCenter - handLength  cos()
Since there are sixty seconds in one minute, the angle for the second hand is
second  (2/60)

66. Drawing Clock, cont. xEnd = xCenter + handLength  sin()
yEnd = yCenter - handLength  cos()
The position of the minute hand is determined by the minute and second. The exact minute value comined with seconds is minute + second/60. For example, if the time is 3 minutes and 30 seconds. The total minutes are 3.5. Since there are sixty minutes in one hour, the angle for the minute hand is
(minute + second/60)  (2/60)

67. Drawing Clock, cont. xEnd = xCenter + handLength  sin()
yEnd = yCenter - handLength  cos()
Since one circle is divided into twelve hours, the angle for the hour hand is
(hour + minute/60 + second/(60  60)))  (2/12)

68. Event-Driven Programming
Procedural programming is executed in procedural order.
In event-driven programming, code is executed upon activation of events.

69. Events
An event can be defined as a type of signal to the program that something has happened.
The event is generated by external user actions such as mouse movements, mouse button clicks, and keystrokes, or by the operating system, such as a timer.

70. Event Information id: A number that identifies the event.
target: The source component upon which the event occurred.
arg: Additional information about the source components.
x, y coordinates: The mouse pointer location when a mouse movement event occurred.
clickCount: The number of consecutive clicks for the mouse events. For other events, it is zero.
when: The time stamp of the event.
key: The key that was pressed or released.

71. Event Classes

72. Selected User Actions Source Event Type User Action Object Generated
Clicked on a button JButton ActionEvent
Changed text JTextComponent TextEvent
Double-clicked on a list item JList ActionEvent
Selected or deselected an item JList ItemEvent with a single click
Selected or deselected an item JComboBox ItemEvent

73. The Delegation Model

74. Selected Event Handlers
Event Class Listener Interface Listener Methods (Handlers) ActionEvent ActionListener actionPerformed(ActionEvent)
ItemEvent ItemListener itemStateChanged(ItemEvent)
WindowEvent WindowListener windowClosing(WindowEvent)
windowOpened(WindowEvent)
windowIconified(WindowEvent)
windowDeiconified(WindowEvent)
windowClosed(WindowEvent)
windowActivated(WindowEvent)
windowDeactivated(WindowEvent)
ContainerEvent ContainerListener componentAdded(ContainerEvent)
componentRemoved(ContainerEvent)

75. Example 10.7 Handling Simple Action Events
Objective: Display two buttons OK and Cancel in the window. A message is displayed on the console to indicate which button is clicked, when a button is clicked.
Run

76. Example 10.8 Handling Window Events
Objective: Demonstrate handling the window events. Any subclass of the Window class can generate the following window events: window opened, closing, closed, activated, deactivated, iconified, and deiconified. This program creates a frame, listens to the window events, and displays a message to indicate the occurring event.
Run

77. Example 10.9 Multiple Listeners for a Single Source
Objective: This example modifies Example 10.7 to add a new listener for each button. The two buttons OK and Cancel use the frame class as the listner. This example creates a new listener class as an additional listener for the action events on the buttons. When a button is clicked, both listeners respond to the action event.
Run