Transform a List<Object> to a Map such that the String is not a duplicate value using Java 8 Streams

Question

We have a Student class as follows:

class Student {
    private int marks;
    private String studentName;

    public int getMarks() {
        r         


        

Answer 1

You can use Collectors.groupingBy(classifier,mapFactory,downstream) method for this purpose:

List list = List.of(
        new Student("abc", 30),
        new Student("Abc", 32),
        new Student("ABC", 35),
        new Student("DEF", 40));

Map map = list.stream()
        .collect(Collectors.groupingBy(
                Student::getStudentName,
                () -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER),
                Collectors.summingInt(Student::getMarks)));

System.out.println(map); // {abc=97, DEF=40}