ZCW-PhoneBook/PhoneBook.java

 
import java.util.*;
/**
 * Created by leon on 1/23/18.
 */
public class PhoneBook {
    //private String name;
    //private String phoneNum;
    TreeMap<String, String> phoneListByName = new TreeMap();
    TreeMap<String, String> phoneListByNum = new TreeMap();
    
    public void add(String name, String phoneNumber){
        phoneListByName.put(name, phoneNumber);
        phoneListByNum.put(phoneNumber, name);
        
    }
    public void remove(String name){
        String phoneNumber = lookUp(name);
        phoneListByName.remove(name);
        phoneListByNum.remove(phoneNumber);
    }
    public String lookUp(String name){
       return phoneListByName.get(name); 
       
    }
    public String reverseLookUp(String phoneNumber){
       return phoneListByNum.get(phoneNumber); 
       
    }
    public void display(){
        Set set = phoneListByName.entrySet();
        //Set set2 = phoneListByNum.entrySet();
        Iterator i = set.iterator();
        
        while(i.hasNext()){
            Map.Entry name = (Map.Entry)i.next();
            System.out.println(name.getKey() + ": " + name.getValue()) ;
        }
    }
}