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Getting the Set with the most elements nested in a HashMap using Java Streams


Getting the Set with the most elements nested in a HashMap using Java Streams

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Getting the Set with the most elements nested in a HashMap using Java Streams
Tag : java , By : Si Gardner
Date : December 05 2020, 12:18 PM

this will help
So my question is: How can I get, using Java Streams, the date that got the most 'YES'.
/* Returns the date that got the most 'YES' votes */
public Optional<LocalDateTime> getWinningDate() {
    return votes.entrySet() // Set<Entry<LocaleDateTime, Set<Vote>>
            .stream() // Stream<Entry<LocaleDateTime, Set<Vote>>
            .flatMap(e -> e.getValue().stream().filter(a -> a.getVote() == VoteType.YES)
                         .map(x -> e.getKey())) // Stream<LocalDateTime>
           .collect(groupingBy(Function.identity(), counting())) // Map<LocaleDateTime, Long>
           .entrySet() // Set<Entry<LocaleDateTime, Long>>
           .stream() // Stream<Entry<LocaleDateTime, Long>>
           .max(Comparator.comparingLong(Map.Entry::getValue)) // Optional<Entry<LocaleDateTime, Long>>
           .map(Map.Entry::getKey); // Optional<LocalDateTime>
}
LocalDateTime winningDate = getWinningDate().orElse(null);
LocalDateTime winningDate = getWinningDate().orElse(defaultDate);
LocalDateTime winningDate = getWinningDate().get();

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How to iterate nested for loops referring to parent elements using Java 8 streams?


Tag : java , By : paolodm
Date : March 29 2020, 07:55 AM
hope this fix your issue When you need both values and want to use flatMap (as required when you want to perform a short-circuit operation like findFirst), you have to map to an object holding both values
response.getFirstNodes().stream()
  .flatMap(first->first.getSndNodes().stream()
    .map(snd->new AbstractMap.SimpleImmutableEntry<>(first, snd)))
  .filter(e->e.getValue().isValid())
  .findFirst().ifPresent(e-> {
    result.setKey(e.getKey().getKey());
    result.setContent(e.getValue().getContent());
  });
response.getFirstNodes().stream()
  .flatMap(first->first.getSndNodes().stream()
     .filter(snd->snd.isValid())
     .map(snd->new AbstractMap.SimpleImmutableEntry<>(first, snd)))
  .findFirst().ifPresent(e-> {
    result.setKey(e.getKey().getKey());
    result.setContent(e.getValue().getContent());
  });

Hashmap with Streams in Java 8 Streams to collect value of Map


Tag : java , By : Ken
Date : March 29 2020, 07:55 AM
Hope this helps If you are sure you are going to get at most a single element that passed the filter (which is guaranteed by your filter), you can use findFirst :
Optional<List> o = id1.entrySet()
                      .stream()
                      .filter( e -> e.getKey() == 1)
                      .map(Map.Entry::getValue)
                      .findFirst();
List<List> list = id1.entrySet()
                     .stream()
                     .filter(.. some predicate...)
                     .map(Map.Entry::getValue)
                     .collect(Collectors.toList());

How to iterate nested for loops referring to parent elements using Java 8 Streams and Lambdas?


Tag : development , By : ArmHead
Date : March 29 2020, 07:55 AM
this one helps. I have the below piece of Code. , I have figured out the solution to my problem.
public static ModuleKey getDeployableModuleFromModulesList(List<Module> modules) {
    Optional<ModuleKey> op = modules.stream().filter(module -> module.getArtifacts().stream().anyMatch(artifact -> artifact.getType().equals("ear"))).map(module -> module.getKey()).findFirst();
    if (!op.isPresent()) {
        op = modules.stream().filter(module -> module.getArtifacts().stream().anyMatch(artifact -> artifact.getType().equals("war"))).map(module -> module.getKey()).reduce((a, b) -> b);
    }
    return op.orElse(null);
}

How to sum elements of an ArrayList which are values of a HashMap using java streams?


Tag : java , By : user182203
Date : March 29 2020, 07:55 AM
hope this fix your issue The first solution that came to my mind was to use mapToDouble and sum.
That would have looked like this:
public static HashMap<Integer, Double> findIncomes(HashMap<Integer, List<Element>> mapa) {
    HashMap<Integer, Double> sumsByKey = new HashMap<>();
    mapa.entrySet().stream().forEach(entry -> sumsByKey.put(entry.getKey(), entry.getValue().stream().mapToDouble(element -> element.getPrice()).sum()));
    return sumsByKey;
}
public static HashMap<Integer, Double> findIncomes(HashMap<Integer, ArrayList<Element>> mapa){
    HashMap<Integer, Double> sumsByKey = new HashMap<>();
    mapa.entrySet().stream().forEach(entry -> sumsByKey.put(entry.getKey(),
        entry.getValue().stream().map(element -> BigDecimal.valueOf(element.getPrice())).reduce(BigDecimal.ZERO, BigDecimal::add).doubleValue()));
    return sumsByKey;
}

Java 8- Lambda expression and streams to iterate over HashMap of HashMap


Tag : java , By : user177910
Date : March 29 2020, 07:55 AM
hope this fix your issue If you want to modify the existing map, you don't need streams. Just loop and call removeIf():
sensor_tags.values().forEach(
        m -> m.keySet().removeIf(datekey.getTime()::after));
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