Map.Entry是同时遍历key和value两个用的

 Map<String, List<TabletRef>> assignMap = new HashMap<String, List<TabletRef>>();

 Set<Map.Entry<String, List<TabletRef>>> assignSet = assignMap.entrySet();

  for (Map.Entry<String, List<TabletRef>> assign : assignSet) {
            String tabletServer = assign.getKey();
            List<TabletRef> localTabletRefs = assign.getValue();
 }