Bug 103927 [build path] External jar Dialog cannot set both Javadoc Location and Java Source Attachment in one iteration
Add an external jar to the project. From the context menu of the jar select properties. Select Javadoc location, browse to the desired location. Select Java Source Attachment. Browse to an external file. Press OK. From the context menu of the jar select properties again. Javadoc location is empty. (At this point it can be entered again without problems)
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/LibrariesWorkbookPage.java
IResource resource= elem.getResource();
				if (resource instanceof IFile) {
					res.add(resource.getFullPath());
				}
			}
		}
		return (IPath[]) res.toArray(new IPath[res.size()]);
	}	
	
	private CPListElement newCPLibraryElement(IResource res) {
		return new CPListElement(fCurrJProject, IClasspathEntry.CPE_LIBRARY, res.getFullPath(), res);
	}
	private CPListElement[] openExtJarFileDialog(CPListElement existing) {
		if (existing == null) {
			IPath[] selected= BuildPathDialogAccess.chooseExternalJAREntries(getShell());
			if (selected != null) {
				ArrayList res= new ArrayList();
				for (int i= 0; i < selected.length; i++) {
					res.add(new CPListElement(fCurrJProject, IClasspathEntry.CPE_LIBRARY, selected[i], null));
				}
				return (CPListElement[]) res.toArray(new CPListElement[res.size()]);
			}
		} else {
			IPath configured= BuildPathDialogAccess.configureExternalJAREntry(getShell(), existing.getPath());
			if (configured != null) {
				return new CPListElement[] { new CPListElement(fCurrJProject, IClasspathEntry.CPE_LIBRARY, configured, null) };
			}
		}		
		return null;
	}