Articles related to : Java 8 streams

The Collectors.teeing() collects stream elements twice concurrently, produces two results, and then uses the specified function to merge them into one final object.

The Collectors.collectingAndThen() allows collect the stream elements and add another (finishing) transformation to the result. It is especially useful for creating multi-level groups using Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.toUnmodifiableList/Set/Map() collectors create corresponding unmodifiable (elements cannot be added o removed) structure. That is why such a collector especially useful for creating multi-level groups using Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.filtering() collector does two things at the same time: selects (filters) some of stream element and collects the results into one structure. That is why such a collector especially useful for creating multi-level groups using Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.reducing() collector does two things at the same time: transforms each stream element and collects the results into one structure. That is why such a collector especially useful for creating multi-level groups using Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.flatMapping() collector does two things at the same time: transforms each element into a stream of values and assembles the result. That is why such a collector especially useful as a parameter when a collector is created by Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.mapping() collector does two things at the same time: transforms each element and assembles the results. That is why such a collector especially useful as a parameter when a collector is created by Collectors.groupingBy() or Collectors.partitioningBy().

The Collectors.partitioningBy() collector breaks the stream elements in two groups – one contains elements that fit the specified criteria and another one that contains elements that do not fit the specified criteria.

Creating a Map object from Stream elements using Collectors.groupingByConcurrent() yields better performance (than .groupingBy())) while processing a parallel stream.

Creating a Map object from Stream elements using Collectors.toConcurrentMap() yields better (than .toMap()) performance while processing a parallel stream.