Java Reference
In-Depth Information
<param name
= Y
value
=
30
/>
</applet>
</body>
</html>
To read the parameter from the applet, use the following method defined in the
Applet
class:
public
String getParameter(String parametername);
This returns the value of the specified parameter.
The applet is given in Listing 18.5. A sample run of the applet is shown in Figure 18.6.
L
ISTING
18.5
DisplayMessage.java
1
import
javax.swing.*;
2
3
public class
DisplayMessage
extends
JApplet
{
4 @Override
/** Initialize the applet */
5 {
6
// Get parameter values from the HTML file
7 String message =
public void
init()
getParameter(
"MESSAGE"
)
;
getParameter
getParameter(
"X"
)
8
int
x = Integer.parseInt(
);
9
int
y = Integer.parseInt(
getParameter(
"Y"
)
);
10
11
// Create a message panel
12 MessagePanel messagePanel =
new
MessagePanel(message);
13 messagePanel.setXCoordinate(x);
14 messagePanel.setYCoordinate(y);
15
16
// Add the message panel to the applet
17 add(messagePanel);
18 }
19 }
add to applet
F
IGURE
18.6
The applet displays the message
Welcome to Java
passed from the HTML
page.
The program gets the parameter values from the HTML file in the
init
method. The val-
ues are strings obtained using the
getParameter
method (lines 7-9). Because
x
and
y
are
int
s, the program uses
Integer.parseInt(string)
to parse a digital string into an
int
value.
If you change
Welcome to Java
in the HTML file to
Welcome to HTML
, and reload the
HTML file in the Web browser, you should see
Welcome to HTML
displayed. Similarly, the
x
and
y
values can be changed to display the message in a desired location.
Caution
The
Applet
's
getParameter
method can be invoked only after an instance of the
applet is created. Therefore, this method cannot be invoked in the constructor of the
applet class. You should invoke it from the
init
method.
