Java Stream converter Map to List

Question

Java Stream converter Map to List

I have this object filled in:

    Map<String, List<LogLine>> logMap = new TreeMap<>();

And after making a filter I would like a flat list of it, but I can only create List List

List<List<LogLine>>  foo = logMap.entrySet().stream()
            .filter(map -> map.getValue().size() > parameters.getThreshold())
            .map(map -> map.getValue())
            .collect(Collectors.toList());

How can I create only one list with all loglines using stream? I tried to use flatMap, but the compiler does not let.

0

java map lista stream collection

Author: Andre, 2017-12-20

Source

1 answers

score 1 · Accepted Answer

I believe the operator you want is flatMap:

List<LogLine> foo = logMap.entrySet().stream()
                .filter(map -> map.getValue().size() > parameters.getThreshold())
                .flatMap(map -> map.getValue().stream())
                .collect(Collectors.toList());

It substitues the current stream [logMap.entrySet().stream()] by a new stream produced by applying a mapper function to each element [map.getValue().stream()].