Advanced programming ch1

Advanced Programming
AWT and Swing
Gera
2020
1

Features of Java
➢Simple
➢Platform independent
➢Architectural Neutral
➢Portable
➢Multithreading
➢Networked
➢Distributed
2
➢High performance
➢Interpreted
➢Dynamic
➢Secured
➢Robust
➢Object Oriented Programming
Language

Features of Java…
Simple:
• Java is simple because of the following factors.
1. Java is free from pointers (i.e) java program does not contain pointers
concept hence we can achieve faster development of the program, faster
execution of the program. Whenever we write a java program that
program is internally converted into pointer program simplicity in
developing the code.
2. Java contains the in-built Garbage Collector program for improving the
performance of a java program.
• Garbage Collector: A Garbage collector is a system java program which
executes in the background along with regular java program for collecting
unused memory locations for improving performance.
3. Java contains user friendly syntaxes for quick development of program.
3

Features of Java…
Platform independent:
• A program is said to be platform independent if that program will run on all available
operating systems without considering their providers.
• -> The languages like c/cpp comes under plotform dependent since,
i) the data types of c/cpp takes different amount of memory space on different
os’s.
ii) the s/w c/cpp does not contain any special programs to convert one format of
one o.s to another format of another o.s.
• Note: DOS operating system understands Mozarta format whereas UNIX operating system
understands embedded linking format[elf].
• ->The language Java is treated as plotform independent language since the data types of
java takes same amount of memory space on all available operating systems.
• -> The s/w JDK[Java development kit] is containing the special programs which converts
from one format of one o.s to another format of another o.s.
• ->The slogan of Java is “Write once and reuse ( or) run anywhere”.
4

Features of Java…
Architectural Neutral:
• If any program runs (or) processed by all available processors
then that program is known as architectural neutral program.
• ->The languages like c/cpp comes under architectural dependent
programs, whereas, “Java” and “.net ” comes under architectural
neutral languages.
Portable:
• A program is said to be portable if which can execute on all
available OS’s and processed by all available processors without
considering their providers and architectures.
• Portability= Plot independent + Architectural Neutral
5

Features of Java…
Multithreading:
• Thread:- flow of control is called a thread.(flow of execution).
• A program is said to be multithreaded program if in which there exists multiple flow of controls and all such flow of
controls executed concurrently & simultaneously.
• ->The languages like c and cpp are treated as single threaded modeling languages.
• -> A single threaded modeling language is one in which there exists single flow of control.
• ->All single thread modeling languages executes the program sequentially and whole execution time is more.
Hence industry is not recommending to implement distributed applications with single threaded modeling
languages.
• -> The languages like “Java” and “.net” are treated as multithreaded modeling language since there exists multiple
flow of controls.
• -> Multitasking is the one specialized form of Multithreading. When we write any Java program there exists two
types of threads. They are
• i) background thread ii)foreground thread.
• -> A background thread is one which always monitors the status of foreground thread.
• -> A foreground thread is one which always executes user defined subprograms/functions. In Java environment,
background thread will exists only one time whereas foreground thread can exists either one ( or) many times.
6

Features of Java…
Networked:
• Java is networked programming language.
• A network is a collection of interconnected autonomous/non autonomous
computers for sharing the data.
• -> We have two categories of networks they are:
• I) Trusted Networks.
• Ii) Untrusted Networks.
• ->A Trusted network is one which is the collection of interconnected autonomous
computers with, trusted network architecture we can develop internet (or)
distributed applications.
• ->An Untrusted network is one in which there exists a collection of interconnected
non-autonomous computers, with untrusted network architecture we can develop
intranet ( or) centralized applications.
• Conclusion: The s/w Java contains the predefined API[library] for developing
network related applications.
7

Features of Java…
Distributed:
• A distributed program is one which runs in the context of
www/browser. Every distributed application can be accessed across
the Globe.
• E.g.:-servlets, jsp, ejb comes under distributed applications.
• High Performance:
• Java is high performance language since
i) Every Java program is internally executing with pointer
notation, whose execution time is very less.
• Java s/w contains one internal program called Garbage collector which
improves the performance of a java program by collecting unused
memory locations.
8

Features of Java…
Robust:
• Java is a Robust language since runtime errors can be processed
effectively.
• Eg: runtime error:10/0;
• Some of the runtime errors are division by zero problems, invalid
bounds of the array.
• Invalid formats of the number etc;
• “runtime errors” in Java are called “Exceptions”.
9

Features of Java…
Object Oriented Programming:
• Java is Object oriented programming language.
• In Information technology we have 2 types of programming models. They are:
i)Procedure oriented programming languages.
ii)Object oriented programming languages.
• ->Procedure oriented programming languages are those which will not provide security to
the data which is represented.
• Hence they are not recommended to develop internet applications.
• E.g.: C, PASCAL, COBOL, FOXPRO, etc.;
• -> Object oriented programming languages are those which provides security to the data
which we represent.
• E.g.: Ada, ALGOL, Small talk, C++, object-
• COBOL, object-PASCAL, Java, .NET etc.; ->The languages like Java and .NET provides 100%
security to the data which we represent, whereas other language like C++ may not be
providing 100% security. Hence the language cpp is not a pure object oriented
programming language.
10

AWT (Abstract Window Toolkit)
CUI(Character User Interface):-
In this we use the characters or commands to interact with
the application. The main disadvantage in CUI is that the
user has to remember several commands and their correct
syntax
CUI is not user friendly.
GUI(Graphics User Interface):-
The environment where the user can interact with an
application through graphics or images is called GUI.
11

AWT…
Advantages:-
1. User friendly
2. It adds attraction and beauty to an application by
adding pictures, colors, menus, animations etc.
3. GUI helps to create graphical components like push
buttons, radio buttons, check boxes, etc. and use them
effectively in our program.
12

AWT…
AWT:-
Abstract Window Toolkit(AWT) represents a class library to
develop applications using GUI.
The java.awt package got classes and interfaces to develop GUI
and let the users interact in a more friendly way with the
application.
Some important classes of java.awt package.
13

AWT…
Components:-
A component represents an object which is displayed pictorially on
the screen.
E.g.:- object of button class can be created Button b=new Button();
b is an object of button class. If we display this b on screen, it displays a
push button.
Therefore the object b, on going to the screen is becoming a component
called “push button”.
In the same way, any component is a graphical representation of
an object. Push buttons, radio buttons, check boxes, etc. are all
components.
14

AWT…
Window:- A window represents any imaginary rectangular area
on the screen, without any borders or title bar.
A frame represents a window with some title and borders In some
applications we create frames to represent various screens
where the user can type some data for the application and output
screens where the result may be displayed in a particular form.
Such screens are nothing but frames only.
A window is a frame without borders and title, whereas a frame
contains borders and title.
15

AWT…
Uses of frames:-
• To draw some graphical shapes like dots, lines,
rectangles etc.
• To display some text in the frame.
• To display pictures or images in the frame.
• To display components like push buttons, radio
buttons etc. in the frame.
16

AWT…
Creating a frame:-
A frame becomes the basic component in AWT. The frame has to
be created before any other component. The reason is all the
other components can be displayed in a frame.
3 ways to create a frame.
Create a frame class object,
1. Frame f=new Frame(); Create a frame class object, and pass
its title also
2. Frame f=new Frame(“My Frame”); Create a subclass myframe
to Frame class and create an object to that subclass
3. Class myframe extends Frame myframe f=new myframe();
17

AWT…
Creating a frame:-…
Since my frame is subclass of Frame it contains a copy of
Frame class and f represents frame.
A frame with 0 pixels width and 0 pixels height will be
created, which is not visible on the screen
A pixel(picture element) represents any single point or
dot on the screen.
Any data or picture which is displayed on the screen is
composed of several dots called pixels.
18

AWT…
Creating a frame:-…
• Monitors will accommodate total 800 pixels horizontally and 600
pixels vertically.
• Total pixels seen on one screen is 800*600 pixels. (4,80000).
This is called screen resolution.
We should increase frame size. This is done by
setSize() method as
f.setSize(300,400);
then display the frame
using setVisible() method as
f.setVisible(true);
19

AWT (Frame)
1. import java.awt.*;// Example of frame code 1
2. class frame
3. {
4. public static void main (String []args)
5. {
6. //creat frame
7. Frame f=new Frame("My AWT Frame");
8. //or f,steTitle("My AWT Frame");
9. //set size of frame
10. f.setSize(350,400);
11. //display the frame
12. f.setVisible(true);
13. }
14. }
20

AWT…
Event:-
•User wants the push button to perform some
action, clicks on the button. Clicking like this is
called event.
•An event represents specific action done on a
component.
•Clicking , double clicking typing data inside the
component, mouse over etc. are all examples of
events.
21

AWT…
Event delegation:-
• When an event is generated on the component, it cannot listen to
the event. We should add some listener to the component.
• A listener will have some abstract methods.
• When an event is generated by the user on the component, the
event is not handled by the component.
• The component sends (delegates) that event to the listener
attached to it.
• The listener will not handle the event. It hands over(delegates)the
event to an appropriate method.
• Finally the method is executed and the event is handled. This is
called “event delegation model”
22

AWT…
Event delegation:-
The following steps are involved in event delegation model:-
• Attach an appropriate listener to a component. This is done
using addXXXListener() method. To remove a listener, use
removeXXXListener() method.
• Implement the methods of the listener, the one which
handles the event.
• When an event is generated on component, then the method in
step 2 will be executed.
23

AWT…
Closing the frame:-
Frame is also a component.
When we click on its close button it should close.
To close the frame:-
We should attach a listener to the frame component.
All the listeners are available in java. awt. event package.
The most suitable listener to the frame is ‘
WindowListener ’. It can be attached using
addWindowListener() method as
f.addWindowListener(WindowListener obj);
addWindowListener() is a method having a parameter
that is expecting object of windowListener interface
24

AWT…
Closing the frame:-
• Since it is not possible to create an object of interface, we
should create an object to the implemention class of
interface and pass it to the method.
Window Listener interface calls the
Public void windowClosing() method when the frame is
being closed.
Public void WindowClosing(WindowEvent e)
{
System.exit(0);
}
25

AWT (Closing)
1. import java.awt.*; //AWT Simple Closing
2. import java.awt.event.*;
3. class myframe3 extends Frame
4. {
6. {
7. myframe3 f=new myframe3();
8. f.setTitle("Frameee");
9. f.setSize(500,200);
11. //close frame
12. f.addWindowListener(new myclass());
13. }
14. }
15. class myclass extends WindowAdapter
16. {
17. public void windowClosing(WindowEvent e)
18. {
19. System.exit(0);
20. }
21. }
26
1. import java.awt.*; //64 AWT Simple Closing 2
3. class myframe4extends Frame
4. {
6. {
7. myframe4f=new myframe4();
8. f.setTitle("Frame4");
9. f.setSize(500,400);
11. //close frame
12. f.addWindowListener(newWindowAdapter()
13. {
14. public void windowClosing(WindowEvente)
15. {
16. System.exit(0);
17. }
18. });
19. }
20. }

AWT…
Font
• To set some font to the text we use setFont() method of Graphics
class as g. setFont(Font object); this method takes Font class object
which can be created as
• Font f= new Font(“sansSerif”,Font.BOLD,30); sansSerif represents the
font name, font.BOLD represents the font style and 30 represents
the font size in pixels.
There are totally 3 styles that we use
font.BOLD
font.ITALIC
font.PLAIN
• Font name: safe approach is to use a logical font name, one of
• “Times New Roman”, "Serif", "Monospaced",
"Dialog", "DialogInput", "Symbol"
27

AWT…
Displaying text in the frame:-
• To display text or strings in the frame we use drawstring()
method of Graphics class as
g.drawString(“hello”, x,y);
• here string “hello” will be displayed starting from the
coordinates(x,y)
• if we want to set some color we can use
g.setColor(Color.red);
28

AWT…
Color
There are 2 ways to set color in AWT
1. Directly mentioning the needed color name (13 predefined colors) from color class as
: Color.x where x is
• orange, pink, cyan, magenta, yellow, black, blue, white,
gray, lightGray, darkGray, red, green
2. To mention any color by combining the three primary colors: red, green and blue,
while creating color class object as.
color c= new color(r, g, b); r, g, b values changes from 0 to 255.
0 represents no color, 10 represents low intensity and 200 represents high intensity
of color.
Color c=new color(255,0,0)//red color
Color c=new color(255,255,255)//white color
Color c=new color(0,0,0)// black color
29

AWT (Background)
1. //frame with background color and message
2. import java.awt.*;
4. class message extends Frame
5. {
6. message()
7. {
8. addWindowListener(new WindowAdapter()
9. {
10. public void windowClosing
(WindowEvent e)
11. {
12. System.exit(0);
13. }
14. });
15. }
16. public void paint(Graphics g)
30
17. {
18. //set Background
19. this.setBackground(new Color(250,0,2));
20. //set font
21. Font f=new Font ("times new
roman",Font.BOLD+Font.ITALIC,60);
22. g.setFont (f);
23. g.setColor(Color.blue);
24. g.drawString("Hello, How are you",10,80);
25. }
27. {
28. message m=new message();
29. m.setSize(550,300);
30. m.setVisible(true);
31. }
32. }

AWT (Demonstrate Colors)
1. import java.awt.*;
2. import javax.swing.JPanel;
3. public class ColorJPanel extends JPanel
4. {
5. public void paintComponent (Graphics g)
6. {
7. super.paintComponent( g);
8. this.setBackground(Color.WHITE);
9. g.setColor(new Color(255,0,0));
10. g.fillRect(15,25,100,20);
11. g.drawString("Current RGB:"+g.getColor(),130,40);
12. g.setColor(new Color(0.50f,0.75f,0.0f));
13. g.fillRect(15,50,100,20);
15. g.setColor(Color.BLUE);
16. g.fillRect(15,75,100,20);
18. Color color = Color.MAGENTA;
19. g.setColor(color);
20. g.fillRect(15,100,100,20);
21. g.drawString("RGB
values:"+color.getRed()+","+color.getGreen()+","+color.getBlue(),130,115);
22. }
23. }
31
1. import javax.swing.JFrame;
2. public class ShowColors
3. {
5. {
6. JFrame frame = new JFrame ("Using colors");
7. frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
8. ColorJPanel colorJPanel = new ColorJPanel();
9. frame.add(colorJPanel);
10. frame.setSize(400, 180);
11. frame.setVisible(true);
12. }
13. }

AWT…
Push buttons:-
Button class is useful to create push buttons. A push
button is useful to perform a particular action.
• To create a push button with a label we can create an
object to button class as
• Button b= new Button();//a button without any label is
created.
• Button b= new Button(“label”);//a button with label is
created.
• To get the label of the button use getLabel();
string l= b.getLabel();
32

AWT…
Push buttons:-…
• To set the label of the button b.setLabel(“label”); Label is
set to button b.
When there are several buttons & a button is clicked & we
have getActionCommand() method of ActionEvent class.
String s= ae.getActionCommand();
S is label of button.
To know source object which is clicked, we can use
getSource() of ActionEvent class as
Object obj=ae.getSource();
33

AWT…
Push buttons:-…
this. setLayout(null);
“this” represents current class object. Since the current
class mybuttons is a subclass of frame class we know
that mybuttons class object has a copy of frame
class
object within it. So any frame class methods can be
invoked using this.
So the setLayout method can be called using
this.setLayout();
34

AWT…
Push buttons:-…
setLayout method is used to set a layout of the
frame.
A layout represents a manner of arranging
components in the frame.
All the layouts are represented as
implementation classes of layoutmanager
interface.
35

AWT (Listeners and Listener methods)
36
Component Listener Listener methods
Button ActionListener public void
actionPerformed(ActionEvent e)
CheckBox ItemListener public void
itemStateChanged(ItemEvent e)
checkBoxGRoup ItemListener public void
TextField ActionListener
focusListener
public void actionPerformed(ActionEvent e)
public void focusGained(ActionEvent e) public void
focusLost(ActionEvent e)
TextArea ActionListener
focusListener
public void
public void focusGained(ActionEvent e) public void
focusLost(ActionEvent e)

37
Choice ActionListener
ItemListener
public void actionPerformed(ActionEvent e)
public void itemStateChanged(ItemEvent e)
List ActionListener
ItemListener
public void
public void
ScrollBar AdjustmentLis
tener
MouseMotionListener
public void
adadjustmentValueChanged(AdjustmentEvent e)
public void mouseDragged(MouseEvent e)
public void mouseMoved(MouseEvente)

38
Frame windowListener Public void
windowActivated(WindowEvent e) Public void
windowClosed(WindowEvent e) Public void
windowClosing(WindowEvent e) Public void
windowDeactivated(WindowEvent e) Public void
windowDeiconified(WindowEvent e) Public void
windowIconified(WindowEvent e)
Public void windowOpened(WindowEvent e)
Key board KeyListener Public void keyPressed(KeyEvent e)
Public void keyReleased(KeyEvent e)
Public void keyTyped(KeyEvent e)
Label No listener is
needed

AWT (Check Boxes)
A check box is a square shaped box which displays an option to the user
• To create checkbox we can create an object to checkbox class as
Checkbox cb= new Checkbox();//checkbox without any label
Checkbox cb= new Checkbox(“label”);//with label
Checkbox cb= new Checkbox(“label”, state);
if state is true check box will appear as if it is selected by default, else not selected.
• To get the state of the checkbox:-
Boolean b=cb.getState();
If the check box is selected this method returns true else false.
• To set the state of checkbox
Cb.setState(true);
• To get the label of check box
String s=cb.getLabel();
39

AWT (Radio Button)
A radio Button represents a round shaped button, such that only one can be selected
from a group of buttons.
Radio buttons can be created using CheckboxGroup class and checkbox classes.
First we should create a CheckboxGroup class object.
• To create a Radio button, pass CheckboxGroup object to Checkbox class object.
CheckboxGroup cbg=new CheckboxGroup();
Checkbox cb=new Checkbox(“label”, cbg, state);
• To know which Radio button is selected by the user
Checkbox cb=cbg.getSelectedCheckbox();
• To know the selected radio button’s label String
label=cbg.getselectedCheckbox().getLabel();
40

AWT (Label)
A Label is a constant text that is generally
displayed along with a TextField or TextArea.
To create a Label:-
Label l= new Label();//create an empty Label.
Label l= new Label(“text”, alignment constraint);
When the label is displayed there would be some
rectangular area allotted for the label.
41

AWT (Label)
A Label is a constant text that is generally
displayed along with a TextField or TextArea.
To create a Label:-
Label l= new Label();//create an empty Label.
Label l= new Label(“text”, alignment constraint);
When the label is displayed there would be some
rectangular area allotted for the label.
42

AWT (Choice class)
• This is useful to display choice menu
Choice ch=new Choice();//create empty choice
• Add item to it using add()
Ch.add(“item”);
• To know the name
String s=ch.getSelectedItem();
• Index of items in the choice menu starts from 0 onwards
Int i=ch.getSelectedIndex();
It returns -1 if nothing is selected.
43

AWT (Choice class)
• To get item String
String item=ch.getItem(int index);
• To know the no of items in choice menu
Int n=ch.getItemCount()
• To remove an item from choice at specified position
Ch.remove(int position)
• To remove an item from choice menu
Ch.remove(String item)
• To remove all items from choice menu
Ch.removeAll()
44

AWT (List class)
This class is useful to create a list box which is similar to
choice menu. A listbox presents the user with a scrolling
list of text items.
The user can select one or more items from the list box.
• To create a list box
List lst=new List();//this stmt creates a list box and
user can select only one item.
• List lst=new List(3);//displays initially 3 rows, the rest
of rows can be seen by clicking on the scroll button
45

AWT (List class)
• List lst=new List(3,true);//this list box displays 3
items, the next parameter true represents the user
can select more than one item from the available
items. If it is false then the user can select only one item.
• To add items to the list box we can use add() as
lst.add(“item”);
• To get all the selected items from the list box
String x[]=lst. getSelectedItems();
46

AWT (List class)
• To get the single selected item
String x=lst. getSelectedItem();
• To get selected items position numbers
Int x[]=lst.getSelectedIndexes();
• To get single selected item position number
Int x=lst. getSelectedIndex();
• To get the no. of visible lines(items)
Int x=lst. getRows();
• To get all the items available in the listbox
String x[]=lst.getItems();
47

AWT (List class)
• To get item name when the position number is known
String item=lst.getItem(int index);
• To know how many no. of items are there
Int x=lst.getItemCount();
• To remove an item at specified position
lst.remove(int position);
• To remove an item whose name is given
lst.remove(String item);
• To remove all the items from the list.
lst.removeAll();
48

AWT (Scrollbar class)
Scrollbar class is useful to create scrollbars that can be attached to a frame
or text area. Scrollbars are used to select continuous values b/w a specified
minimum and maximum.
Scrollbars can be arranged vertically or horizontally.
To create a Scrollbar
Scrollbar sb=new
Scrollbar(alignment,start,step,min,max);
Here,
Alingnment:Scrollbar.VERTICAL,
Scrollbar.HORIZONTAL
Start: starting value (Ex:0)
Step: step value(Ex:30)//represents scrollbar 49

To create a Scrollbar…
length
Min: minimum value (Ex:0)
Max: maximum value (Ex:300)
• To know the location of Scrollbar we can use getValue() that
gives the position of scrollbar in pixels, as:
Int n=sb.getValue();
• To update the scrollbar position to a new
position, we can use setValue() method as:
Sb.setValue(int position); 50

To create a Scrollbar…
• To get maximum value of the scrollbar:
Int x= sb.getMaximum();
• To get the minimum value of the scrollbar:
Int x=sb.getMinimum();
• To get the alignment of the scrollbar:
Int x=getOrientation();
This method returns zero if the scrollbar is aligned horizontally
and returns one if it is aligned vertically.
51

References
➢S. Horstmann and Gary Cornell, Core Java 2 – Volume II-
Advanced Features, Sun Microsystems Press
➢Harvey M. Deitel and Paul J. Deitel, Java How to
Program, Deitel & Associates
52
Gerabirhan Paulos
ToCourseInfo@gmail.com

Advanced programming ch1

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