ZCW-PhoneBook/PhoneBook.java

import java.util.*; 

/**
 * Created by leon on 1/23/18.
 */
public class PhoneBook {
    String name;
    String phoneNumber;
    SortedMap<String, String> phoneBook = new TreeMap<String, String>();
    
    public void add(String name, String phoneNumber){
        phoneBook.put(name, phoneNumber);
    }
    
    public void remove(String name){
        phoneBook.remove(name);
    }
    
    public String lookup(String name){
        return phoneBook.get(name);
    }
    
    public String reverseLookup(String phoneNumber){
        for(Map.Entry<String, String> e : phoneBook.entrySet()){
            if(e.getValue().equals(phoneNumber)){
                return e.getKey();
            }
        }
        return null;
    }
    
    public void display(){
        System.out.printf("%-20s%-12s\n", "Name", "Phone Number");
        for(Map.Entry<String, String> e : phoneBook.entrySet()){
            String printName = e.getKey();
            String printNumber = e.getValue();
            System.out.printf(" %-20s %-12s\n", printName, printNumber);
        }
        System.out.printf("-----End of the phone book-----\n");
    }
}