Creating an Optional The Optional<T> class models the absence of a value by a special singleton returned by the Optional.empty()…
Multilevel Partitioning Like the groupingBy() method, the partitioningBy() operation can be used in multilevel classification. The downstream collector in a…
Collecting to an Array The overloaded method toArray() can be used to collect or accumulate into an array. It is…
Consumer Action on Stream Elements We have already used both the forEach() and forEachOrdered() terminal operations to print elements when…
Collecting to a Collection The method toCollection(Supplier) creates a collector that uses a mutable container of a specific Collection type…
Implementing Functional Reduction: The reduce() Method A functional reduction combines all elements in a stream to produce a single immutable…
Finding the First or Any Element The findFirst() method can be used to find the first element that is available…
Summary of Terminal Stream Operations The terminal operations of the Stream<T> class are summarized in Table 16.5. The type parameter…
16.8 Collectors A collector encapsulates the functions required for performing reduction: the supplier, the accumulator, the combiner, and the finisher.…
Multilevel Grouping The downstream collector in a groupingBy() operation can be created by another groupingBy() operation, resulting in a multilevel…