How do i get string list of username and fullname from firebase?

[Vora Ravi]

In java class i used some random username and fullname for testing but now i want to get the list of username and full name of user who are child of current user in Mates node in firebase.

public class User
{

   public String fullname;
   public String username;



   public User() {
   }

   public User(String fullname, String username) {
       this.fullname = fullname;
       this.username = username;
   }



   public String getFullname() {
       return fullname;
   }

   public String getUsername() {
       return username;
   }


   public static List<User> USERS = Arrays.asList(

           new User("Priya Jain", "priya_98"),
           new User("Manoj Patel","manoj_34"),
           new User("Akbari Mayur", "mayur897"),
           new User("Tushar Khabri", "khbri90")
   );


}

I want replace this user to firebase user who is child of current user, here i put link of database image.

https://i.stack.imgur.com/CxOux.jpg