Bug 55884 Loading a user library from file does not warn when overwriting an existing library [build path]
Works in I2004032400010 + plug-in export for I200403240800 Add library 'mylib'. Save it. Change it. Load library from file. ==> should warn that 'mylib' gets changed.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/UserLibraryPreferencePage.java
private void updateUserLibararies(IProgressMonitor monitor) throws CoreException {
		
		List list= fLibraryList.getElements();
		HashSet oldNames= new HashSet(Arrays.asList(JavaCore.getUserLibraryNames()));
		int nExisting= list.size();
		
		for (int i= 0; i < nExisting; i++) {
			CPUserLibraryElement element= (CPUserLibraryElement) list.get(i);
			oldNames.remove(element.getName());
		}	
		
		int len= nExisting + oldNames.size();
		monitor.beginTask(PreferencesMessages.getString("UserLibraryPreferencePage.operation"), len); 
		MultiStatus multiStatus= new MultiStatus(JavaUI.ID_PLUGIN, IStatus.OK, PreferencesMessages.getString("UserLibraryPreferencePage.operation.error"), null); 
		
		ClasspathContainerInitializer initializer= JavaCore.getClasspathContainerInitializer(JavaCore.USER_LIBRARY_CONTAINER_ID);
		IJavaProject jproject= getDummyProject();
		
		ArrayList paths= new ArrayList();
		ArrayList urls= new ArrayList();
		
		for (int i= 0; i < nExisting; i++) {
			CPUserLibraryElement element= (CPUserLibraryElement) list.get(i);
			IPath path= element.getPath();
			IClasspathContainer oldContainer= JavaCore.getClasspathContainer(path, jproject);
			if (oldContainer == null || element.hasChanges(oldContainer)) {
				IClasspathContainer updatedContainer= element.getUpdatedContainer();
				try {