search for the average via streamapi

how to use the api stream to find the average grade in a given subject for all students?
Allow in Hashmap<String, String > map

For example: key: "Ann", value: "Physics 3.5 Math 4.0 History 2.5"

class Student {
private String name;
private Map<String, List<Integer>> marks;
public Student(String name, Map<String, List<Integer>> marks) {
this.name = name;
this.marks = marks;
}
public String getName() {
return name;
}
public Map<String, List<Integer>> getMarks() {
return marks;
}
public static void main(String[] args) {
Map<String, List<Integer>> markAnn = new HashMap<>();
markAnn.put("Physics", List.of(4, 4, 5));
markAnn.put("Mathematics", List.of(2, 3, 4));
markAnn.put("History", List.of(3, 3, 3));
Map<String, List<Integer>> markKate = new HashMap<>();
markKate.put("Physics", List.of(1, 2, 3));
markKate.put("Mathematics", List.of(5, 5, 3));
markKate.put("History", List.of(4, 2, 5));
Student[] students = {new Student("Ann", markAnn),
new Student("Kate", markKate)
};
}
}

As I understood you need a method that`s finds all averages in subjects for student. So you can create method like findAverage:

 public static Map<String, List<Integer>> findAverage(Map<String, List<Integer>> students){
return students.entrySet()
.stream()
.collect(Collectors.toMap(
Map.Entry::getKey,
entry -> Collections.singletonList(
(int) entry.getValue().stream().mapToInt(Integer::intValue).average().orElse(0)
)
));
}

The method returns Map<String, List<Integer>> with value like:

{Mathematics=[4], History=[3], Physics=[2]}

than you can add it to your collection.

Student[] students = {new Student("Ann", findAverage(markAnn)),
new Student("Kate", findAverage(markKate))
};

Note that could be some situations when the average could be 4.3 or 3.5. So if you need it. You can change types to double whenever you want by using mapToDouble() instead mapToInt()