Could Not Find the Main Class: HelloWorld. Program will Exit

Question

Possible Duplicate:
.jar file keeps giving me “ could not find the main class”. Program will exit

Trying to run a basic "hello World" program. I have followed step by step tutorials and i get the same error message each time:

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)
Exception in thread "main"

Here is the Program:

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

Has anyone had this same issue and know how to resolve it?

How (or are) you setting your classpath? – Dave Newton Jun 04 '12 at 18:02 — Dave Newton, Jun 04 '12 at 18:02
what is the command you're using to run the program? – Dan Jun 04 '12 at 18:05 — Dan, Jun 04 '12 at 18:05

score 0 · Answer 1 · answered Jun 04 '12 at 18:09

Is the this is the tutorial you are following: http://docs.oracle.com/javase/tutorial/getStarted/cupojava/win32.html ?

If not, try to do that one and see if you get the same result.

Also, try to run your application as follows:

C:\java.exe yourjavaprogram.Main

Or you can google the error and you will probably find the solution faster than you think :)

score 0 · Answer 2 · answered Jun 04 '12 at 18:10

0

Did you compile the program? In command prompt type javac HelloWorld.java This will make a .class file in the same folder. Now type java HelloWorld should work.

answered Jun 04 '12 at 18:10

Aleksandr Vasilenko

13
5

score 0 · Answer 3 · answered Jun 04 '12 at 18:48

Make sure your java file is in a package which lives in a "source folder" in Eclipse parlance. That means the icon should look like an open folder containing an orange-ish square with a plus-shape superimposed on it, and the HelloWorld.java file should have a solid blue J on the document icon. If the folder icon just looks like a regular folder, and/or the java file has an outlined J on it, Eclipse won't even compile that code.

Could Not Find the Main Class: HelloWorld. Program will Exit

3 Answers3