ZCW-PhoneBook/PhoneBook.java

 import java.util.*;


/**
 * Created by leon on 1/23/18.
 */
public class PhoneBook {
    TreeMap<String, String> phoneListName = new TreeMap();
    TreeMap<String, String> phoneListNumber = new TreeMap();

    public void add(String name, String number){
        phoneListName.put(name, number);
        phoneListNumber.put(number, name);
    }
 
    public void remove(String name){
        String number = lookUp(name);
        phoneListName.remove(name);
        phoneListNumber.remove(number);
    }
    
    public String lookUp(String name){
        return phoneListName.get(name);
    }
    
    public String reverseLookUp(String number){
        return phoneListNumber.get(number);
        
    }
    
    public void display(){
        Set set = phoneListName.entrySet();
        Iterator i = set.iterator();
        
        while(i.hasNext()){
            Map.Entry me = (Map.Entry)i.next();
            System.out.println(me.getKey() + ": " + me.getValue());
        }
        
    }
    
    
}