collecting data with streams

Collectors are used to gather the results of a stream into useful data structures or summarized values. Java provides the Collectors utility class with operations such as toList, toSet, joining, groupingBy, partitioningBy, and counting. In this section, you’ll learn how to transform stream results into collections, maps, groups, and statistical summaries. You’ll also see how multiple collectors can be combined to solve more complex data-processing problems. These techniques are especially useful when working with real-world business data.