how to iterate Map>> in java?

Question

I have a method which is returning Map<String, List<Map<String, Object>>>

How to iterate over a map like Map<String, List<Map<String, Object>>>

Probably this is answered here: http://stackoverflow.com/questions/46898/how-to-efficiently-iterate-over-each-entry-in-a-map#46908 — Alexander Arutinyants, Jan 22 '17 at 12:03
What do you need to do while iterating over this map? What have you tried so far? — Tim Biegeleisen, Jan 22 '17 at 12:03
There is List> inside of Map.There I am Confusing to iterate — Sai Kishore Mani, Jan 22 '17 at 12:04
Someone's trying to help you. Mindless repeating your question doesn't help anyone. — shmosel, Jan 22 '17 at 12:09
There is absolutely nothing confusing about it. Iterate over the map as usual. If you wish to iterate over the inner list, do that, if you want to iterate over the nested map again, do it - just nest your basic iterations. — luk2302, Jan 22 '17 at 12:15

Michael Ritter · Answer 1 · 2017-01-22T12:15:31.533

You would iterate over it like you would iterate over every other map. You just need to "recursively" iterate over the List and another Aap inside the iteration loop.

One possible way (without functional code):

Map<String, List<Map<String, Object>>> yourMap = ...;
//iterate over outer map
for(Map.Entry<String, List<Map<String, Object>>> topEntry : yourMap.entrySet()) {
  String topKey = topEntry.getKey();
  //iterate over list
  for(Map<String, Object> innerMap : topEntry.getValue()) {
    //iterate over inner map
    for(Map.Entry<String, Object> innerEntry : innerMap.entrySet()) {
      String innerKey = innerEntry.getKey();
      Object innerValue = innerEntry.getValue();
    }
  }
}

You can also switch the foreach loop iterating over the List to a fori loop [ for(int i=0; i<list.size(); i++) ] if you need to know the list-index.

And what is that error? did you define the map or is it just null? — Michael Ritter, Jan 22 '17 at 15:21

how to iterate Map>> in java?

1 Answers1