How to apply Filtering on groupBy in java streams

Question

How do you group first and then apply filtering using Java streams?

Example: Consider this Employee class: I want to group by Departme

Answer 1

Java 8 version: You can make grouping by Department and then stream the entry set and do the collect again with adding the predicate in filter:

    Map> collect = list.stream()
        .collect(Collectors.groupingBy(Employee::getDepartment)).entrySet()
        .stream()
        .collect(Collectors.toMap(Map.Entry::getKey,
            entry -> entry.getValue()
                .stream()
                .filter(employee -> employee.getSalary() > 2000)
                .collect(toList())
            )
        );