The groupingBy() method of Collectors class in Java are used for grouping objects by some property and storing results in a Map instance. In order to use it, we always need to specify a property by which the grouping would be performed. This method provides similar functionality to SQL’s GROUP BY clause.
public static Collector<T, ?, Map<K, List>> groupingBy(Function classifier)
Type Parameter: This method takes two type paramters:
Parameters: This method accepts two mandatory parameters:
Return value: It returns a collector as a map.
Below is the program implementation of groupingBy() method:
Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.