Bug 15301 'show in packages view' - does not work fo java files not in source folders
20020502 open a java file that is in a resource folder (so it is not an ICompilationUnit - just a file with .java extension) 'show in packages view' is present in the context menu but it does nothing
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/viewsupport/BaseJavaElementContentProvider.java
try {
			if (element instanceof IJavaModel) 
				return getJavaProjects((IJavaModel)element);
			
			if (element instanceof IJavaProject) 
				return getPackageFragmentRoots((IJavaProject)element);
			
			if (element instanceof IPackageFragmentRoot) 
				return getPackageFragments((IPackageFragmentRoot)element);
			
			if (element instanceof IPackageFragment) 
				return getPackageContents((IPackageFragment)element);
				
			if (element instanceof IFolder)
				return getResources((IFolder)element);
			
			if (fProvideMembers &&
				element instanceof ISourceReference && element instanceof IParent) {
				if (element instanceof ICompilationUnit && fProvideWorkingCopy) {
					IWorkingCopy wc= getWorkingCopy((ICompilationUnit)element);
					if (wc != null)
						return ((IParent)wc).getChildren();
				}
				return ((IParent)element).getChildren();
			}
		} catch (JavaModelException e) {
			return NO_CHILDREN;
		}		
		return NO_CHILDREN;	
	}