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Package – Class
(application programming interface)
import javax.swing.JOptionPane;
method
String
JOptionPane.showInputDialog("Cash: ");
javax.lang
Class
This package will be imported by default
double
argument
method argument
Double.parseDouble(str);
Cash = Double.parseDouble(
JOptionPane.showInputDialog("Cash: ")
);
http://java.sun.com/j2se/1.4.2/docs/api/index.html
1
String class, equals method
String Answer; // Answer is an object of class String;
boolean IsHappy;
Answer = JOptionPane.showInputDialog(
"Are you happy? (Y for yes, others for N) " );
//
//
//
//
//
The following condition doesn’t work
if (Answer == ("Y" || "y" )
if (Answer == "Y" || Answer == "y" )
IsHappy = true;
if (Answer.equals("Y“) || Answer.equals("y"))
IsHappy = true;
else
IsHappy = false;
2
Cosmetics & HTML
Cosmetics :
Tools or material to make up faces
= Face + (????)
HTML : HyperText Markup Language
Tools or material to make up hypertext document
HTML Document = Hypertext + HTML Tags
3
Text and HyperText
Mathematicians and Philosophers
by Chung-Chih Li
Rene Descartes:
<html>
<body>
<h1> Mathematicians and Philosophers </h1>
<div class="author">by Chung-Chih Li </div>
"I am thinking, therefore I exist."
Descartes was the most important figure in
modern mathematics and philosophy, and this
probably is the most famous say of Descartes;
but what does it really mean? The existence
is established necessarily via mankind's
awareness, which seemed self-evidence to
Descartes, but some obvious objections
followed immediately. You may want to see
the excellent debate in Meditations on First
Philosophy edited by John Cottingham --,
which is a collection of Descartes'
Meditations, their objections, and Descartes'
replies.
<h3> Rene Descartes: </h3>
<h4> "I am thinking, therefore I exist.“
</h4>
Descartes was the most important figure in
.......
<h4> "The brain is a machine. " </h4>
</body>
</html>
"The brain is a machine."
http://hal.lamar.edu/~licc/math_phi_s2.html
4
Static HTML
IE
need file20
click
file6,
file9,
file100,
…….
file1, file2, file3, file4,
file5, file6, file7, file8,
file9, file10, file11, file12,
file13, file14, ………….
………………..
………………..
………………..
………………..
………………..
………………..
File server
need file34
click
Internet
Client
Server
5
Dynamic HTML
file1, file2, file3, ..
quiz.html
…….
Progrma1….
cgi-bin/generic-grader.pl
………………..
data1, data2, date3, 1022
………………..
IE
<form name=“x” method=“post”
action="http://cs.colgate.edu/cgibin/generic-grader.pl"
I.E
….. 100 out of 100 are
correct..
result.html
generic-grader.pl
</form>
answers.txt
file server
? quiz.html
answers.txt
Form x …….
? answers.txt
Internet
Client
Server
6
HTML Web browser (IE, Netscape)
Running a Java Application in your Web browser
--- which means, an HTML document can run a program
-- Big deal?? YES, Big deal.
•
What kinds of machines? (100 kinds!!)
Java uses Virture Machine
(bytecodes) HelloWorld.class
•
Security and safety.
Java provides strong security environment
7
Pigglet:
Applet:
Pigglet is a little pig
who is Pooh’s best friend.
An applet is a little application
who is Web’s best friend.
Running a Java Application in your Web browser
--- which means, an HTML document can
have a running program
Tic-Tac-Toe Applet example
Many more on
C:/Program Files/j2sdk_nb/j2sdk1.4.2/demo/applets
8
An html document with Java applet
<html>
<head>
<title> TicTacToe v1.1 </title>
</head>
<body> <h1> TicTacToe v1.1 </h1>
<hr>
<applet code=TicTacToe.class width=120 height=120>
</applet>
<a href="TicTacToe.java">The source.</a>
</body></html>
9
Your next assignment
<HTML>
<body>
<h>COSC 1373-01/Java, Sprint 2004</h>
This is an applet.
<APPLET code="Asg3.class" width=350 height=200>
</APPLET>
<a href="Asg3.java">The source.</a>
<h3> by Your name here </h3>
</body>
</HTML>
Asg3.html
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Java 2 supported Web browsers
1. Netscape 7
2. I.E. with Java Plug-in
1. install
Java 2 Running time environment. (J2RE)
j2re-1_4_0-win.exe
2. or go to
http://www.java.com/en/download/windows_automatic.jsp
for automated Java Plug-in installation
3. under window command mode:
appletviewer Asg3.html
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Classes:
A class is a concept of something
Vehicle
color, wheels, seat, engine……..… .(Attributes)
can run, turn, stop, carry things ……(Methods)
Truck
big wheels, diesel engine, cargo deck...(Attributes)
…lift cargo deck…………………………(Methods)
Truck extends the concept of Vehicle
Applet
(some people knows what an Applet should be)
Asg3
(We want them all but modify or add a little.)
Asg3 extends the concept ofApplet
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Class
Objects
instantiation
Vehicle
SUV
Honda Pilot
Drive
instantiation
I J
000-AAA
Integer I,J;
I = new Integer(3);
J = new Integer(9);
Object
Number
Double
011-JAV
Integer
int i,j;
i = Integer.parseInt(“1”);
j = I.parseInt(“1”);
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An applet
import java.awt.Graphics;
import javax.swing.JApplet;
//
//
//
//
import class Graphics in
java.awt package
(Abstract Windows Toolkit)
import class JApplet
public class TestApplet extends JApplet {
public void paint( Graphics g )
{
super.paint( g );
g.drawString( "Welcome to Java Programming!", 40, 40 );
}
} // end class TestApplet
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Typical applet components
import java.awt.Graphics;
import javax.swing.JApplet;
//
//
//
//
import class Graphics in
java.awt package
(Abstract Windows Toolkit)
import class JApplet
public class App extends JApplet {
public void init() {
} // This will be executed 1st
public void start() {
} // then this, 2nd
public void paint( Graphics g ) {
public void stop() {
} // then this. 3rd
}
public void destroy() {
}
} // end class App
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Some Terminologies
Drawing: putting anything on the
screen of the applet. images, text (String),
buttons, graphics (line, dots, circle..)
primitives.
Event handling: detecting and processing
anything caused by the user (or other
programs)
Applets inherit the methods in some classes of java.awt
package to handle drawing and event handling.
16
What Applets Can't Do
(for security reasons)
1. Cannot read or write files.
2. Cannot make network connections except to
where it came from.
3. Cannot start other program.
4. Cannot detect certain system properties.
17
Graphics class
import java.awt.Graphics;
import java.awt.Color;
// import class Graphics
// import class Color
Some useful methods of Graphics and a field of Color.
g.drawString("I can draw!!", 50, 150);
g.drawRect(30,30, 200, 100);
g.setColor(Color.blue);
g.drawArc(100, 20, 100, 100, 0, 120);
g.drawArc(0, 0, 100, 100, 0, 275);
g.setColor(Color.green);
g.fillRect(60,60, 10,20);
g.setColor(Color.red);
g.drawOval(150,100, 200, 100);
g.setColor(Color.yellow);
g.fillOval(200, 130, 90, 50);
Test Applet
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