How to use thenComparing in java stream

问题

I have a map with strings as values. I want to sort it firstly by length, and if length of the strings is the same, i want to sort it alphabetic. I wrote those code :

String out = outMap.values().stream()
                .sorted(Comparator.comparing(e -> e.length()).thenComparing()...)
                .collect(Collectors.joining());

The problem is, when i am writing thenComparing, I couldn't use e.length() anymore. How can i fix it?

EDIT : Map<Character, String> . I want to sort the strings and make one string in output by concat all of them.

回答1:

How about

String out = outMap.values().stream()
        .sorted(Comparator.comparingInt(String::length)
                          .thenComparing(Comparator.naturalOrder()))
                    //OR  .thenComparing(String.CASE_INSENSITIVE_ORDER))
        .collect(Collectors.joining());

来源：https://stackoverflow.com/questions/48796108/how-to-use-thencomparing-in-java-stream