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/ClasspathContainerWizard.java
}
			if (containerPage == null)	{
				containerPage= new ClasspathContainerDefaultPage();
			}
			
			containerPage.setSelection(fEntryToEdit);
			fContainerPage= containerPage;
			addPage(containerPage);
		}
		super.addPages();
	}
	
	private void handlePageCreationFailed(CoreException e) {
		String title= NewWizardMessages.getString("ClasspathContainerWizard.pagecreationerror.title"); 
		String message= NewWizardMessages.getString("ClasspathContainerWizard.pagecreationerror.message"); 
		ExceptionHandler.handle(e, getShell(), title, message);
	}
	
	
	private ClasspathContainerDescriptor findDescriptorPage(ClasspathContainerDescriptor[] containers, IClasspathEntry entry) {
		for (int i = 0; i < containers.length; i++) {
			if (containers[i].canEdit(fEntryToEdit)) {
				return containers[i];
			}
		}
		return null;
	}			
	
}