Can I run from command line program created by Ecl

Question

Using Eclipse I have created a SWT Hello World program. I was able to run this program from Eclipse and it worked fine.

In the "/home/myname/workspace/HelloWorldSWT" I found two files: HelloWorldSWT.java and HelloWorldSWT.class. I wanted to execute the corresponding program from the command line. First I tried to type "java HelloWorld" and I got the following error message:

Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld
   at gnu.java.lang.MainThread.run(libgcj.so.90)
Caused by: java.lang.ClassNotFoundException: HelloWorld not found in gnu.gcj.runtime.SystemClassLoader{urls=[file:./], parent=gnu.gcj.runtime.ExtensionClassLoader{urls=[], parent=null}}
   at java.net.URLClassLoader.findClass(libgcj.so.90)
   at gnu.gcj.runtime.SystemClassLoader.findClass(libgcj.so.90)
   at java.lang.ClassLoader.loadClass(libgcj.so.90)
   at java.lang.ClassLoader.loadClass(libgcj.so.90)
   at gnu.java.lang.MainThread.run(libgcj.so.90)

I also tried this "java -cp /home/roman/workspace/ HelloWorld.HelloWorld". As the result I got the following error message:

Exception in thread "main" java.lang.NoClassDefFoundError: loaded class HelloWorld.HelloWorld was in fact named HelloWorld
   at java.lang.VMClassLoader.defineClass(libgcj.so.90)
   at java.lang.ClassLoader.defineClass(libgcj.so.90)
   at java.security.SecureClassLoader.defineClass(libgcj.so.90)
   at java.net.URLClassLoader.findClass(libgcj.so.90)
   at gnu.gcj.runtime.SystemClassLoader.findClass(libgcj.so.90)
   at java.lang.ClassLoader.loadClass(libgcj.so.90)
   at java.lang.ClassLoader.loadClass(libgcj.so.90)
   at gnu.java.lang.MainThread.run(libgcj.so.90)

Does anybody know what I am doing wrong? Thank you in advance for any help.

Answer 1

Seems to me you don't have a class named HelloWorldSWT``, but rather a class named HelloWorldSWT in a package named HelloWorldSWT (you can confirm this by going at the first line of HellowWorldSWT.java, where you will find package HelloWorldSWT;

If so, go in parent directory and type

java HelloWorldSWT.HelloWorldSWT This would work.

Answer 2

I do some workaround so as to take full advantage of the Eclipse convenience. Below is what I found, and it worked well for me. Hope it will help:

Answer 3

It is possible that you are not loading the SWT library correctly, and as a result your class fails to load.

The SWT library is part of jars that are already loaded when you run Eclipse but are not loaded in a command line parameter. Did you modify your class path accordingly?

Here is an old article about how to do this sort of stuff in older versions of Eclipse http://www.ibm.com/developerworks/opensource/library/os-ecgui1/ You will need different jars today with latest version fo Eclipse. It might even come down to a single jar.

Check out the SWT FAQ; at least for Mac Carbon, you can use a single jar, I would bet you can do that for other platforms.

Also, I'm not 100% sure that you can run Eclipse under openJDK, which seems to be the case on your platform.