Java Reference
In-Depth Information
To run the program you type the command
java HelloWorld
This executes the main method of HelloWorld . When you run the program,
it displays
Hello, world
Now you have a small program that does something, but what does it
mean?
The program declares a class called HelloWorld with a single member: a
method called main . Class members appear between curly braces { and
} following the class name.
The main method is a special method: the main method of a class, if de-
clared exactly as shown, is executed when you run the class as an ap-
plication. When run, a main method can create objects, evaluate expres-
sions, invoke other methods, and do anything else needed to define an
application's behavior.
The main method is declared public so that anyone can invoke it (in this
case the Java virtual machine)and static , meaning that the method be-
longs to the class and is not associated with a particular instance of the
class.
Preceding the method name is the return type of the method. The main
method is declared void because it doesn't return a value and so has no
return type.
Following the method name is the parameter list for the methoda se-
quence of zero or more pairs of types and names, separated by commas
and enclosed in parentheses ( and ) . The main method's only paramet-
 
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