question: public static IPackageFragmentRoot addClassFolder ( IJavaProject jproject , String containerName , IPath sourceAttachPath , IPath sourceAttachRoot ) throws CoreException { IProject project = jproject . getProject ( ) ; IContainer container = null ; if ( containerName == null || containerName . length ( ) == 0 ) { container = project ; } else { IFolder folder = project . getFolder ( containerName ) ; if ( ! folder . exists ( ) ) { CoreUtility . createFolder ( folder , false , true , null ) ; } container = folder ; } IClasspathEntry cpe = JavaCore . newLibraryEntry ( container . getFullPath ( ) , sourceAttachPath , sourceAttachRoot ) ; addToClasspath ( jproject , cpe ) ; return jproject . getPackageFragmentRoot ( container ) ; }
target:  Creates and adds a class folder to the class path.