Filter in Java 8 threads

Question

I tried to filter entries in a HashMap using the Streams API, but was stuck in the last method call Collectors.toMap. So I have no hint for implementing the toMap method

    public void filterStudents(Map<Integer, Student> studentsMap){
            HashMap<Integer, Student> filteredStudentsMap = studentsMap.entrySet().stream().
            filter(s -> s.getValue().getAddress().equalsIgnoreCase("delhi")).
            collect(Collectors.toMap(k , v));
    }

public class Student {

        private int id;

        private String firstName;

        private String lastName;

        private String address;
    ...

    }

Any suggestions?

Answer 1

Just generate the output Mapfrom the key and the values ​​of the records that pass your filter:

public void filterStudents(Map<Integer, Student> studentsMap){
    Map<Integer, Student> filteredStudentsMap = 
        studentsMap.entrySet()
                   .stream()
                   .filter(s -> s.getValue().getAddress().equalsIgnoreCase("delhi"))
                   .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
}