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group all keys with same values in a hashmap java

Zany Zebra answered on August 24, 2020 Popularity 4/10 Helpfulness 2/10

answer group all keys with same values in a hashmap java

group all keys with same values in a hashmap java

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Map<String, ArrayList<Integer>> reverseMap = new HashMap<>();

for (Map.Entry<Integer,String> entry : map.entrySet()) {
    if (!reverseMap.containsKey(entry.getValue())) {
        reverseMap.put(entry.getValue(), new ArrayList<>());
    }
    ArrayList<Integer> keys = reverseMap.get(entry.getValue());
    keys.add(entry.getKey());
    reverseMap.put(entry.getValue(), keys);
}

Popularity 4/10 Helpfulness 2/10 Language java

Source: stackoverflow.com

Tags: group hashmap java

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