Java 8 stream map to list of keys sorted by values
You say you want to sort by value, but you don't have that in your code. Pass a lambda (or method reference) to sorted
to tell it how you want to sort.
And you want to get the keys; use map
to transform entries to keys.
List<Type> types = countByType.entrySet().stream()
.sorted(Comparator.comparing(Map.Entry::getValue))
.map(Map.Entry::getKey)
.collect(Collectors.toList());
You can sort a map by value as below, more example here
//Sort a Map by their Value.
Map<Integer, String> random = new HashMap<Integer, String>();
random.put(1,"z");
random.put(6,"k");
random.put(5,"a");
random.put(3,"f");
random.put(9,"c");
Map<Integer, String> sortedMap =
random.entrySet().stream()
.sorted(Map.Entry.comparingByValue())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
(e1, e2) -> e2, LinkedHashMap::new));
System.out.println("Sorted Map: " + Arrays.toString(sortedMap.entrySet().toArray()));
You have to sort with a custom comparator based on the value of the entry. Then select all the keys before collecting
countByType.entrySet()
.stream()
.sorted((e1, e2) -> e1.getValue().compareTo(e2.getValue())) // custom Comparator
.map(e -> e.getKey())
.collect(Collectors.toList());