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java map get key by index

marktecher.com answered on October 2, 2022 Popularity 8/10 Helpfulness 5/10

answer java map get key by index

java map get key by index

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// Note that for Hashmaps the order of the elements kinda "random"
// it depends on the hash function
KeyType firstKey = map.keySet().stream().findFirst().get();
ValueType value = map.get(firstKey);

// If you want to get first item by insertion order use LinkedHashMap
Map<KeyType, ValueType> map = new LinkedHashMap<>();
map.put(firstIndexItemKey, firstIndexItemValue);
map.put(secondIndexItemKey, secondIndexItemValue);

// If you want to maintain sorted by values Map, consider the TreeMap
Map<KeyType, ValueType> map = new TreeMap<>();

// If you want to use Unmodifiable HashMap and have it ordered once 
// and forvever without any further insertions, you can use this trick
public static Map<Integer, Integer> sortByKey(Map<Integer, Integer> map) {
    List<Map.Entry<Integer, Integer>> list = 
      						new ArrayList<>(map.entrySet());
    list.sort(Comparator.comparingInt(Map.Entry::getKey));
    Map<Integer, Integer> sortedMap = new LinkedHashMap<>();
    list.forEach(e -> sortedMap.put(e.getKey(), e.getValue()));
    return Collections.unmodifiableMap(sortedMap);
}

Popularity 8/10 Helpfulness 5/10 Language java

Source: stackoverflow.com

Tags: get java key map

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Contributed on Oct 02 2022

marktecher.com

0 Answers Avg Quality 2/10

java map get key by index

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