CODEWITHSUNDEEP
javaandroidlistarraylisthashmap
Newbie
Newbie

Reputation: 1714

Convert HashMap of HashMap into ArrayList of ArrayList

I know convert HashMap into List can be done by List<String> list = new ArrayList<>(hashMap.values());, But how about HashMap of HashMap?

Like: HashMap<String, HashMap<String, String>>, how to convert it into ArrayList<ArrayList<String>>?

My idea so far is List<List<String>> list = new ArrayList(hashMap.values());, but how to convert inner HashMap into list with/without iterate it?

Upvotes: 2

Views: 2615

Answers (3)

Pavneet_Singh
Pavneet_Singh

Reputation: 37404

For non-java 8 you can use

1.) Fetch entry set from your hashMapOfMaps

2.) hashMapOfMaps.getValue() will retrun HashMap<String, String> and then .values() return the String values of inner map

    for (Entry<String, HashMap<String, String>> entry:  hashMapOfMaps.entrySet()) {
        listOfLists.add(new ArrayList<String>(entry.getValue().values()));
    }                                                 |            |
                                                   inner-Map       |
                                                                   |
                                                      inner-Map's string values

Upvotes: 2

Murat Karag&#246;z
Murat Karag&#246;z

Reputation: 37584

Since you want this on android you might not want to use Java 8 streams. Here for JDK 7

HashMap<String, HashMap<String, String>> mapOpfMap = new HashMap<>();
List<List<String>> listOfList = new ArrayList<>();

Iterator<Map.Entry<String, HashMap<String, String>>> it = mapOpfMap.entrySet().iterator();
    while(it.hasNext()){
        Map.Entry<String, HashMap<String, String>> value = it.next();
        value.getKey(); // here is the key if you need it
        listOfList.add(new ArrayList<>(value.getValue().values()));
    }

Upvotes: 0

john16384
john16384

Reputation: 8044

map.values().stream()  // a stream of Map<String, String>
    .map(innerMap -> new ArrayList<>(innerMap.values())  // a stream of List<String>
    .collect(Collectors.toList());  // List of List<String>

Of course, you lose all key information.

Upvotes: 2

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