Grouping by object value, counting and then setting group key by maximum object attribute

by

Here’s one approach. First group into lists and then process the lists into the values you actually want:

import static java.util.Comparator.comparingLong;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toMap;


Map<Route,Integer> routeCounts = routes.stream()
        .collect(groupingBy(x -> x))
        .values().stream()
        .collect(toMap(
            lst -> lst.stream().max(comparingLong(Route::getLastUpdated)).get(),
            List::size
        ));

More Related Contents:

  1. How to group objects when each object could go in multiple groups?
  2. How to convert to Java 8 map grouping by Map [closed]
  3. Java 8 List into Map
  4. Convert Iterable to Stream using Java 8 JDK
  5. Using Java 8’s Optional with Stream::flatMap
  6. Collection to stream to a new collection
  7. In Java, what are the advantages of streams over loops? [closed]
  8. Java 8’s streams: why parallel stream is slower?
  9. Stream and lazy evaluation
  10. Java 8 stream’s .min() and .max(): why does this compile?
  11. How do I keep the iteration order of a List when using Collections.toMap() on a stream?
  12. Why is this java Stream operated upon twice?
  13. Files.walk(), calculate total size
  14. Is it possible to use the Java 8 Stream API on Android API < 24?
  15. How do I create a Stream of regex matches?
  16. Simplest way to print an `IntStream` as a `String`
  17. Sort map by value using lambdas and streams
  18. Iterate two Java-8-Streams together [duplicate]
  19. Why parallel stream get collected sequentially in Java 8
  20. In Stream reduce method, must the identity always be 0 for sum and 1 for multiplication?
  21. Close Java 8 Stream
  22. How to check if exists any duplicate in Java 8 Streams?
  23. Finding enum value with Java 8 Stream API
  24. How to implement a Java stream?
  25. Why didn’t Stream have a toList() method?
  26. Picking elements of a list until condition is met with Java 8 Lambdas
  27. BigDecimal summary statistics
  28. Nested Java 8 parallel forEach loop perform poor. Is this behavior expected?
  29. non-interference requirement on Java 8 streams
  30. Parallel flatMap always sequential

Leave a Comment