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/packageview/PackageExplorerPart.java
void restoreFilters() {
		IMemento filtersMem= fMemento.getChild(TAG_FILTERS);
		if(filtersMem != null) {	
			IMemento children[]= filtersMem.getChildren(TAG_FILTER);
			String filters[]= new String[children.length];
			for (int i = 0; i < children.length; i++) {
				filters[i]= children[i].getString(TAG_ELEMENT);
			}
			getPatternFilter().setPatterns(filters);
		} else {
			getPatternFilter().setPatterns(new String[0]);
		}
		
		String show= fMemento.getString(TAG_SHOWLIBRARIES);
		if (show != null)
			getLibraryFilter().setShowLibraries(show.equals("true")); 
		else
			initLibraryFilterFromPreferences();
	}
	
	void initFilterFromPreferences() {
		initLibraryFilterFromPreferences();
	}
	void initLibraryFilterFromPreferences() {
		JavaPlugin plugin= JavaPlugin.getDefault();
		boolean show= plugin.getPreferenceStore().getBoolean(TAG_SHOWLIBRARIES);
		getLibraryFilter().setShowLibraries(show);
	}
	
	boolean isExpandable(Object element) {