I have developed an swing application using XML config file. i have used jdom. for development i had the jdom.jar file in the class path. when i executed the app: $ java MyFrame it worked fine. then i bundled the compiled class files in a jar file indiwiz.jar (with appropriate manifest file), & execute: $ java -jar indiwiz.jar the exception thrown is: Exception in thread "main" java.lang.NoClassDefFoundError: org/jdom/input/SAXBuilder jdom.jar is still in the classpath. why is this error being thrown?