#465 Grouping Students by Group Number

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Themes:

JavaStreams & LambdasPractice

A list of Student objects is given. Each student contains a name and a group number. Create a map where:

Key: group number;
Value: the list of students belonging to that group.

class Student {
    String name;
    Integer group;
}

List<Student> students = Arrays.asList(
    new Student("Ivan", 1),
    new Student("Alex", 1),
    new Student("Nikita", 3),
    ...
);

Example of obtaining students by group from the created Map:

// map.get(1) = [Student("Ivan", 1), Student("Alex", 1)]
// map.get(3) = [Student("Nikita", 3)]
Map<Integer, List<Student>> map = ...

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