CODEWITHSUNDEEP
javahashmap
Abdel-Rahman
Abdel-Rahman

Reputation: 569

is there a way to get values of a map of pair and value by the key pair only?

I have this map static Map<Pair<String,Integer>, Integer> wordTopic = new HashMap<>(); Basically it's a matrix , and i want all the values of specific string(the key of the pair)..AKA all the values of one row..

This will get the sum of one row ,but i have no idea how to get the row itself,each value all in an array or something.

   wordTopic.entrySet()
                .stream()
                .filter(e -> e.getKey().getKey().equals(key))
                .mapToInt(Map.Entry::getValue)
                .sum();

Upvotes: 1

Views: 1144

Answers (2)

Haroun Mohammedi
Haroun Mohammedi

Reputation: 2424

You just have to add a collector at the end of the stream like that : 

wordTopic.entrySet()
            .stream()
            .filter(e -> e.getKey().getKey().equals(key))
            .mapToInt(Map.Entry::getValue)
            .collect(Collectors.toList());

and here you go

Upvotes: 0

Ousmane D.
Ousmane D.

Reputation: 56433

You can create a method as such:

int[] getValuesByKey(Map<Pair<String,Integer>, Integer> map, String key) {
      return map.entrySet()
                .stream()
                .filter(e -> e.getKey().getKey().equals(key))
                .mapToInt(Map.Entry::getValue)
                .toArray();
}

which given a map and a key will yield all the values where the entry key is equal to the provided key.

or if you want an Integer array then you can do:

Integer[] getValuesByKey(Map<Pair<String,Integer>, Integer> map, String key) {
      return map.entrySet()
                .stream()
                .filter(e -> e.getKey().getKey().equals(key))
                .map(Map.Entry::getValue)
                .toArray(Integer[]::new);
}

or if you want to retrieve a list.

List<Integer> getValuesByKey(Map<Pair<String,Integer>, Integer> map, String key) {
      return map.entrySet()
                .stream()
                .filter(e -> e.getKey().getKey().equals(key))
                .map(Map.Entry::getValue)
                .collect(Collectors.toCollection(ArrayList::new));
}

Upvotes: 4

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