Java 8 grouping using custom collector?

Question

I have the following class.

class Person {

    String name;
    LocalDate birthday;
    Sex gender;
    String emailAddress;

    public int getAge() {
             


        

Answer 1

You can also use Collectors.toMap and provide mapping for key, value and merge function(if any).

Map ageNameMap = 
    members.stream()
            .collect(Collectors.toMap(
              person -> person.getAge(), 
              person -> person.getName(), (pName1, pName2) -> pName1+"|"+pName2)
    );