CODEWITHSUNDEEP
javalisthashmap
Miss_Ann
Miss_Ann

Reputation: 89

How to get List value from map object

I have object value called "mastervalue" from my hashmap. The mastervalue contain ques_id as key, and an array contain score and answer as value. How to get value of the array only(the score and answer) and return as List. 

String maprule = "department == '2' && topic == '1'";

mastervalue = (Map<String, List<String>>) map_master.get(maprule);
System.out.println(mastervalue);

mastervalue print out : {10359=[4, 1], 10365=[1, 1], 10364=[1, 1], 10363=[4, 1], 10362=[3, 1], 10369=[1, 1], 10368=[5, 1]}

Upvotes: 4

Views: 66550

Answers (3)

Eduardo Briguenti Vieira
Eduardo Briguenti Vieira

Reputation: 4599

For Kotlin there is a shortcut:

map.values.flatten()

As the doc states:

Returns a single list of all elements from all collections in the given collection.

Upvotes: 0

Shailendra Madda
Shailendra Madda

Reputation: 21561

For Koltin users here is the way:

val listOfObjects = List<Object>?.stream()?.flatMap { obj: Collection<Object> -> obj.stream() }
                ?.collect(Collectors.toList())

Generic way:

fun <T: Any> listList(list: List<List<KClass<T>>>) = list.stream().flatMap { obj: Collection<*> -> obj.stream() }.collect(Collectors.toList())

Upvotes: 0

Rogue
Rogue

Reputation: 11483

Okay:

public <T> List<T> getValues(Map<?, T> map) {
    return new ArrayList<>(map.values());
}

Inlined:

List<List<String>> list = new ArrayList<>(map_master.values());

Or using the method:

List<List<String>> list = getValues(map_master);

Alternatively, if you want to put all the values of all the lists into one, just iterate:

List<String> total = new ArrayList<>();
for (List<String> lis : map_master.values()) {
    total.addAll(lis);
}

And with Java 8 streams:

List<String> total = map_master.values().stream()
                            .flatMap(Collection::stream)
                            .collect(Collectors.toList());

Upvotes: 25

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