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Collectors.groupingBy method

Collectors.groupingBy is a static method provided by the java.util.stream.Collectors class, typically used in conjunction with stream().collect().^[600-developer-java-java8-java8-collect.md] It implements the Collector interface to perform a mutable reduction operation on stream elements.^[600-developer-java-java8-java8-collect.md]

Method Signatures

The source material outlines two primary overloaded signatures for groupingBy:

  • groupingBy(Function, Collector): This signature takes a classifier function and a downstream collector.
  • groupingBy(Function, Supplier, Collector): This signature includes a supplier function to provide a specific map implementation, in addition to the classifier and downstream collector^[600-developer-java-java8-java8-collect.md].