|
Ben Black
Ben Black has been programming Java for a year. His motto is once you
have learned the basics, you have conquered the language.
He is the main webmaster
of the Java resource site Cookie Nest -
www.cookienest.com.
|
Java Basic - Compiling & Running
If you have chosen to use an IDE to write Java programs
then all the tools needed for you to run, edit and compile the code
are supplied so you wouldn't need to use these techniques of
compiling and running, but you should read it any way since it shows
you how to compile and run your first Java program.
There are two different sort of programs you can make in Java,
applications and applets. Applets are the ones which run in your
browser. Applications are more like programs you run in Windows and
have their own window environment, unlike applets which run in the
same window environment as the browser. I'll show you how to run
both an applet and application in different ways.
I'll start with the application example.
| Hello World Application
Source Code |
public class hello_world
{
public static void main(String[] args)
{
System.out.println("Hello
World");
}
}
|
| Hello World Application Bat
File Code |
javac hello_world.java
java
hello_world
|
|
Download
Files |
What you have just seen is the ultimate program that any
programmer would be happy to write; it is the Hello World
application. Follow these simple steps.
- Select the hello world application source code (or download
it) and paste it in to your text editor.
- Save the file as hello_world.java.
- Select the hello world application bat file code and paste it
in a new page of your text editor.
- Save this file as hello_world.bat (or in fact anything,
but remember to save it as bat file), into the same folder
as hello_world.java file.
- Run hello_world.bat.
And before your eyes (cross fingers) you should see this
happen.
You have just ran your first Java
program. But if it didn't work and all the files were correctly
typed up and in the same folder (if you did type it up yourself, try
downloading them and then trying again), then you might of got this
error.
This means that you haven't set up your
path correctly in the autoexec.bat file. Go back to Getting
Started for information about setting your path correctly.
If it did work I'll better explain how and why it works. The
bat file is just a quick and easier way of compiling and
running your file, you could open up MS-DOS Prompt (Start -->
Programs --> MS-DOS Prompt) and type in.
javac hello_world.java
RETURN
java
hello_world
RETURN
But that means navigating your way to the correct directory where
the java file is and you would have to do it every time you
modify the java file. So instead the bat file does it
for you. (Note: To edit the bat file, right click on
it and select Edit from the menu).
So what is the bat file doing. Firstly it is compiling
hello_world.java by using the java compiler, javac.
When it compiles the file it creates a class file; in this
case it is hello_world.class. Class files are the
files which contain the bytecode needed for someone to see your program.
The java file is the actual Java code which you can see and
edit, but the compiled version, the class file is bytecode
which only the JVM (Java Virtual Machine) can read.
This means that you can just provide the class file (but if
you're a nice kind person you'll also provide the java file,
so that other programmers can see what you have done).
Once you have created the class file you can run it, using
the program java. You shouldn't put the extension on the end
of your file. For example, this wouldn't work.
java hello_world.class
Nor...
java hello_world.java
Instead you should put.
java hello_world
New on the Java Boutique:
New Review:
Time Management Made Easy with the Quartz Enterprise Job Scheduler
Why not just use the Java timer API? This open source scheduling
API boasts simplicity, ease-of-integration, a well-rounded feature
set, and it's free!
New Applet:
Reverse Complement
Reverse Complement is a simple applet that converts DNA or RNA
sequences into three useful formats.
Elsewhere on internet.com:
WebDeveloper Java
Lots of Java information on webdeveloper.com
WDVL Java
Thorough Java resource at the Web Developer's Virtual Library.
ScriptSearch Java
Hundreds of free Java code files to download.
jGuru: Your View of the Java Universe
Customizable portal with online training, FAQs, regular news updates, and tutorials.
