The layout manager you are using with the netbeans GUI builder is not any of the core managers that java provides for you. Basically you are using code provided in a 3rd-party jar file. You will need to make this available in the classpath (using any of the normal techniques for this) when you run the compile command. In this case, I'm not sure what jar file(s) you would need (try a google search) as I've still not found a GUI builder that I like, nor am I up to speed on netbeans specifically.