how sort when hashmap value is list of objects by multiple properties java 8
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Clash Royale CLAN TAG#URR8PPPhow sort when hashmap value is list of objects by multiple properties java 8
Suppose I have like :
Map<String, List<MyState>> map = new HashMap<>();
map.computeIfAbsent(key, file -> new ArrayList<>()).add(myState);
map.put("aa",list1..)
map.put("bb",list2..)
map.put("cc",list3..)
public class MyState {
private String state;
private String date;
}
I want to sort the map values List<MyState> by MyState::date and then by MyState::state
List<MyState>
MyState::date
MyState::state
map entries
HashMap
IMO the original post before the edit was more clear as it was stating you wanted to sort the map values by
getDate then by getState. "I want to sort the map entries" no so clear.– Aomine
31 mins ago
getDate
getState
1 Answer
1
You can do so with:
map.values()
.forEach(l -> l.sort(Comparator.comparing(MyState::getDate)
.thenComparing(MyState::getState)));
Should that be
MyState::getState in the thenComparing block?– christopher
33 mins ago
MyState::getState
thenComparing
@christopher yup, thanks.
– Aomine
32 mins ago
Or
map.forEach((k, l) -> l.sort(yourComparator)) which I think should be faster.– daniu
29 mins ago
map.forEach((k, l) -> l.sort(yourComparator))
@daniu yup that's also another way to go, but I simply avoided that since I am not interested in the map keys as I am sorting the lists.
– Aomine
28 mins ago
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Sorting
map entries:HashMapis not ordered. Also, lists will have multiple entries. Which of the list elements do you use to sort values of the map itself?– ernest_k
33 mins ago