Bug 81426 Package Explorer shows nothing after drill into working set, then show projects
I200412160800 - switch Package Explorer to working sets - context menu > Go Into a working set - Show > Projects -> view is empty -> view toolbar button 'Up to Working Sets' does not do anything
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
Object o= elements[i];
			if (!(o instanceof IJavaElement)) {
				if (o instanceof IResource) {
					IJavaElement jElement= JavaCore.create((IResource)o);
					if (jElement != null && jElement.exists()) 
						elements[i]= jElement;
				}
				else if (o instanceof IAdaptable) {
					IResource r= (IResource)((IAdaptable)o).getAdapter(IResource.class);
					if (r != null) {
						IJavaElement jElement= JavaCore.create(r);
						if (jElement != null && jElement.exists()) 
							elements[i]= jElement;
						else
							elements[i]= r;
					}
				}
			}
		}
		
		return new StructuredSelection(elements);
	}
	
	private boolean containsResources(Object[] elements) {
		for (int i = 0; i < elements.length; i++) {
			Object o= elements[i];
			if (!(o instanceof IJavaElement)) {
				if (o instanceof IResource)
					return true;
				if ((o instanceof IAdaptable) && ((IAdaptable)o).getAdapter(IResource.class) != null)