I'm trying to run a java program that I have written. It's very simple and just processes text, using a single class with just the two methods; it does not depend on anything else apart from an input file. It has compiled fine on this machine, and run on other machines, but when I try to run it on this machine, I get the following: Directory of C:\weka [.] [..] ARFFFormat.class ARFFFormat.java cs239data.txt iris.arff MyClassifier.class MyClassifier.java 6 File(s) 379,912 bytes 2 Dir(s) 11,360,374,784 bytes free C:\weka>java ARFFFormat cs239data.txt Exception in thread "main" java.lang.NoClassDefFoundError: ARFFFormat Caused by: java.lang.ClassNotFoundException: ARFFFormat 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) So java can't find the class file even though it's right there and I just compiled it. Can anybody think what might be going on here? Thanks

I'm not really a Java expert, I've only been programming in it for about a year now, but I think I may be able to help. If you could include the source code, that might make the problem a bit easier to diagnose.

Is class ARFFFormat part of a package? If so, it will need to be in a subdirectory structure that reflects the package name.