Java Reference
In-Depth Information
Chapter 16
Applications and Applets
• See how to make a set of classes into a Java application.
• See how to make an application into an executable file.
• See how to write an applet and put it on an html page.
There are two ways to make a set of Java classes into a unit that can be used else-
where. The first is to build an application , which generally resides on your com-
puter and can be executed when you want. The second is to build an applet , which
can be called when a browser loads an html page.
Java applications
A Java application is a bunch of classes (in .java files) in which (at least) one
class has a method main of the following form:
/** Called by system to start execution of the Java application */
public static void main(String[] args) { … }
The system calls method main to start execution of the program. The param-
eter, a String array, can contain information that the application uses when exe-
cution starts. The parameter is rarely used, and we will not discuss it further. So
if you do not know about arrays, it does not matter.
In DrJava, there is no need for this method main because any static method
in a compiled class, as well as any instance method of an accessible folder, can
be called in the Interactions pane. But in other IDEs, method main is necessary,
and you may have to tell the IDE which class contains method main . Each IDE
has a different way to do this.
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