Bug 4240 Can't edit class path entry (1GKEPIF)
There is no way to edit an existing entry for a library on the Java Build Path project properties page (other than editing the .classpath file directly). NOTES: EG (9/22/2001 11:42:11 AM) this is particularly annoying for variables. we should have an Edit button when a variable is selected.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/LibrariesWorkbookPage.java
try {
				IPath outputLocation= fCurrJProject.getOutputLocation();
				if (outputLocation != null) {
					IResource resource= fWorkspaceRoot.findMember(outputLocation);
					if (resource instanceof IFolder) { 
						res.add(resource);
					}
				}
			} catch (JavaModelException e) {
				
				JavaPlugin.log(e.getStatus());
			}
		}	
			
		List cplist= fLibrariesList.getElements();
		for (int i= 0; i < cplist.size(); i++) {
			CPListElement elem= (CPListElement)cplist.get(i);
			if (elem.getEntryKind() == IClasspathEntry.CPE_LIBRARY) {
				IResource resource= elem.getResource();
				if (resource instanceof IContainer) {
					res.add(resource);
				}
			}
		}
		return (IContainer[]) res.toArray(new IContainer[res.size()]);
	}
	
	private IFile[] getUsedJARFiles() {
		List res= new ArrayList();
		List cplist= fLibrariesList.getElements();