collections, Phone Book class

PhoneBook.java
========================================================================

package PhonePkg;

import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;

public class PhoneBook {
    protected TreeMap<Character, TreeMap<String, Set<String>>> thePhoneBook;

    // get the first letter in the name in upper case
    // if no letters in the name returns *
    private char firstLetter(String name) {
        for (int i = 0; i < name.length(); i += 1) {
            char ch = name.charAt(i);

            if (ch >= 'a' && ch <= 'z') {
                return Character.toUpperCase(ch);
            } else if (ch >= 'A' && ch <= 'Z') {
                return ch;
            }
        }

        // no letters in the name
        return '*';
    }

    // format the name as a key
    // remove leading and trailing spaces and convert to lower case
    private String keyFormat(String name) {
        return name.trim().toLowerCase();
    }

    // build an empty phone book
    public PhoneBook() {
        this.thePhoneBook = new TreeMap<Character, TreeMap<String, Set<String>>>();

        // every letter has no records
        for (char letter = 'A'; letter <= 'Z'; letter += 1) {
            thePhoneBook.put(letter, new TreeMap<String, Set<String>>());
        }

        // for names with no letters
        thePhoneBook.put('*', new TreeMap<String, Set<String>>());
    }

    // add a phone number to a person
    public boolean addPhone(String name, String phone) {
        name = keyFormat(name);

        // get all records starting with the same letter
        TreeMap<String, Set<String>> letterRecords = thePhoneBook
                .get(firstLetter(name));

        // if name is not exist as a key
        if (!letterRecords.containsKey(name)) {
            // add new name (key) with no phone numbers
            letterRecords.put(name, new TreeSet<String>());
        }

        // add the number to person phones set
        return letterRecords.get(name).add(phone);
    }

    // remove a number of person
    public boolean removePhone(String name, String phone) {
        name = keyFormat(name);

        // get all records starting with the same letter
        TreeMap<String, Set<String>> letterRecords = thePhoneBook
                .get(firstLetter(name));

        // if no such name (key)
        if (!letterRecords.containsKey(name)) {
            // return true
            return true;
        }

        // remove number from person numbers
        letterRecords.get(name).remove(phone);

        // if person is without numbers
        if (letterRecords.get(name).isEmpty()) {
            // remove it and return true
            letterRecords.remove(name);
            return true;
        }

        // return true if person or phone does not exist
        return !letterRecords.get(name).contains(phone);
    }

    // return true is person exists (also has numbers)
    public boolean isExist(String name) {
        name = keyFormat(name);

        TreeMap<String, Set<String>> letterRecords = thePhoneBook
                .get(firstLetter(name));

        return letterRecords.containsKey(name);
    }

    // return the phone numbers of an person
    // if not exist returns null
    public Set<String> getPhonesOf(String name) {
        name = keyFormat(name);

        TreeMap<String, Set<String>> letterRecords = thePhoneBook
                .get(firstLetter(name));

        return new TreeSet<String>(letterRecords.get(name));
    }

    @Override
    public String toString() {
        String res = "";

        for (Map.Entry<Character, TreeMap<String, Set<String>>> entry : thePhoneBook
                .entrySet()) {
            if (!entry.getValue().isEmpty()) {
                res += "\n" + entry.getKey() + "\n";

                for (Map.Entry<String, Set<String>> itr : entry.getValue()
                        .entrySet()) {
                    res += itr.getKey() + " --> " + itr.getValue() + "\n";
                }

            }
        }

        return res;
    }
}