import java.util.TreeMap; import java.util.Map; /** * Created by Mexi Liang on 06/11/18. */ public class PhoneBook { String name = ""; String phoneNumber= ""; Map phoneBook = new TreeMap<>(); public void addEntry(String name,String phoneNumber){ phoneBook.put(name, phoneNumber); } public void removeEntry(String name){ phoneBook.remove(name); } public int size(){ return phoneBook.size(); //return size of the phonebook } }