Java 8 stream map to list of keys sorted by values

Question

I have map Map countByType and I want to have a list which has sorted (min to max) keys by their corresponding values. My try is:

Answer 1

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());