ZCW-PhoneBook/PhoneBook.java

/**
 * Created by leon on 1/23/18.
 */
import java.util.*;

public class PhoneBook {
    private TreeMap<String, ArrayList<String>> book = new TreeMap<String, ArrayList<String>>();

    public ArrayList<String> add(String name, String phoneNumber) {
        ArrayList<String> converted = new ArrayList<String>();

        if (book.containsKey(name)) converted = book.get(name);

        converted.add(phoneNumber);
        add(name, converted);
        return book.get(name);
    }

    public ArrayList<String> add(String name, ArrayList<String> phoneNumbers) {
        book.put(name, phoneNumbers);
        return book.get(name);
    }

    public TreeMap<String, ArrayList<String>> remove(String name) {
        book.remove(name);
        return book;
    }

    public ArrayList<String> remove(String name, String number) {
        ArrayList<String> numbers = book.get(name);
        numbers.remove(numbers.indexOf(number));
        book.put(name, numbers);
        return book.get(name);
    }

    public ArrayList<String> lookup(String name) {
        return book.get(name);
    }

    public String reverseLookup(String phoneNumber) {
        String result = "none";
        for(Map.Entry<String, ArrayList<String>> entry : book.entrySet()) {
            ArrayList<String> numbers = entry.getValue();
            for (String number : numbers) {
                if (number.equals(phoneNumber)) result = entry.getKey();
            }
        }
        return result;
    }

    public String display() {
        StringBuilder result = new StringBuilder();
        for(Map.Entry<String, ArrayList<String>> entry : book.entrySet()) {
            result.append(entry.getKey() + " ");

            ArrayList<String> numbers = entry.getValue();
            for (String number : numbers) {
                result.append(number + " ");
            }

            result.append("\n");
        }
        return result.toString();
    }

    public static void main(String[] args) {
        PhoneBook phoneBook = new PhoneBook();
    };
}