Class Not Found command promt

[TenF]

Hi,

I'm not really a beginner in Java, but since I've never worked from the command prompt before, I guess I am a beginner at that ;)

I've been trying to start a Java application from the command prompt, but I keep getting the error message that dhe class could not be found.
I've searched the internet a lot and tested things, but I can't figure out what the problem is. To make things simple I made a Hello World application which gives the same error.

I made the following program, naming it HelloWorld.java and saving it in the directory C:\mywork

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

I then started the command prompt and compiled the program using
javac HelloWorld.java
When I tried to run it using
java HelloWorld
I got the following error message:
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld
Caused by: <list of things>
Could not find the main class: HelloWorld. Program will exit.

What am I missing? Please help. I need to test my application, it's an assignment for school and I have to hand it in in a week...

[TenF]

Ok, I got some help elsewhere, but I don't understand what was wrong. So if someone could explain to me what the problem was, I would be grateful.
The solution was to start the application using the following
java -classpath . HelloWorld

I was told I had to change the CLASSPATH variable to solve the problem permanently, by putting a dot in front of the current CLASSPATH. But the dot was already in place.
Anyone have a clue as to why things are acting this way?

Edit: Oh, and I'm sorry for the double posting, but it is kind of a reply to my earlier message, not an addition or something ;)

[weddy69]

depends on the operating system you have but I believe you just run your jar
java -jar myjar.jar

quick search on this should help a lot.

[TenF]

Thank you for your reply.

However, I don't have any jar-file. I was just working with .java and .class files.

And I did more than a quick search, I did a thorough search.
But as I said, the solution was something that shouldn't have worked. I had checked my classpath, but it seemed fine. So adding "-classpath . " shouldn't have changed anything.

[Mr.Beans]

Print out the entire command line session of you trying to compile/run it so we can see everything.

Here is mine

joe@joe:~/Projects$ ls
cdk  Main.java
joe@joe:~/Projects$ javac Main.java
joe@joe:~/Projects$ ls
cdk  Main.class  Main.java
joe@joe:~/Projects$ java Main
Hello World

Mr. Beans

[TenF]

C:\mywork>javac HelloWorld.java

C:\mywork>java HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld
Caused by: java.lang.ClassNotFoundException: HelloWorld
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: HelloWorld.  Program will exit.

C:\mywork>java -classpath . HelloWorld
Hello World!

C:\mywork>

C:\mywork>path
PATH=C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\system32\WBEM;C:\Program Files\Au
todesk\Maya 8.5 Personal Learning Edition\bin;C:\Program Files\MiKTeX 2.7\miktex
\bin;C:\Program Files\Common Files\Teleca Shared;E:\Programma's\TortoiseSVN\bin;
C:\Program Files\QuickTime\QTSystem\;C:\Program Files\Java\jdk1.5.0_04\bin;E:\Pr
ogramma's\OpenVPN\bin

I noticed that the path doesn't have a dot in front, but if I go to environment variables (properties of My Computer, Advanced tab) the classpath variable does have a dot...

[Spiller]

Tip: Use the command set to see/edit current environment variables from the command line.

Java won't look for classes in the other, ordinary path, though the dot directory is implicit in that, by the way.

[TenF]

So I typed 'set' followed by Enter.
The path is as posted before. The classpath is '. (period)'
no idea what that means.

In what way should I edit which variable?

[Fubarable]

have you tried compiling like so:

javac -cp . HelloWorld.java

(don't forget the period in there)

Edit: also, are you placing your java file in a package and giving it a package name (my guess is not)?

[TenF]

Ok, I tried compiling with the -cp . added
When trying to run the application, I got the same errors, so I still had to add -cp . when running it.

And no, no package.
As I said, I am currently testing with simply a HelloWorld.java, which is really nothing more than a good old fashioned Hello World program. The code of this "program" is in my first post.

And thanks for the replies, I really appreciate you all trying to help :)