Exception in thread main java.lang.NoClassDefFoundError

Writing by on Monday, 12 of October , 2009 at 9:18 pm

After getting used to the spoon-feeding IDE’s, writing some one-off classes might lead to this Exception.

Exception in thread “main” java.lang.NoClassDefFoundError: HelloWorld
Caused by: java.lang.ClassNotFoundException: HelloWorld
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
Could not find the main class: HelloWorld. Program will exit.

Very common problem. Your classpath needs a .: followed by the classpath, to include the class(es) in your current directory.

java -cp .:./lib/mysql.jar HelloWorld

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Shivdev Kalambi's Blog

Shivdev Kalambi is a Software Development Manager, previously a Principal Software Engineer at ArcSight/HP. With over 16 years' experience in software development, he's worked on several technologies and played different roles and contributed to all phases of projects. Non-tech activies include Ping-pong, Rock Climbing and Yoga at PG, Golf, Skiing, Swimming & a beer enthusiast.