ZCW-PhoneBook/PhoneBook.java

 
import java.util.*;
/**
 * Created by leon on 1/23/18.
 */
public class PhoneBook {
    
    Map<String, ArrayList<String> > entries = new HashMap<String, ArrayList<String>>();
    
    public void addEntry(String name, String phoneNumber){
        ArrayList<String> pn = new ArrayList<String>();
        pn.add(phoneNumber);
        this.entries.put(name, pn);
    }
    
    public void addNumberTo(String name, String phoneNumber){
        for(Map.Entry<String, ArrayList<String>> entry: this.entries.entrySet()){
            if(name.equals(entry.getKey())){
                entry.getValue().add(phoneNumber);
                break;
            }
        }    
    }
    
    public void removePhoneNumber(String name, String phoneNumber){
        for(Map.Entry<String, ArrayList<String>> entry: this.entries.entrySet()){
            if(name.equals(entry.getKey())){
                int indexOf = entry.getValue().indexOf(phoneNumber);
                if(indexOf >= 0){
                    entry.getValue().remove(indexOf);
                    break;
                }
            }
        }        
    }
    
    public void removeRecord(String name){
        this.entries.remove(name);
    }
    
    public String lookUp(String name){
        StringBuilder sb = new StringBuilder();
        for(Map.Entry<String, ArrayList<String>> entry: this.entries.entrySet()){
            if(entry.getKey().equals(name)){
                for(String pn : entry.getValue()){
                    sb.append(pn);
                }   
            }
        }
        return sb.toString();        
        
    }
    
    public String reverseLoopup(String phoneNumber){
        String name = null;
        for(Map.Entry<String, ArrayList<String>> entry: this.entries.entrySet()){
            for(String pn : entry.getValue()){
                if(pn.equals(phoneNumber)){
                    name = entry.getKey();
                }
            }
        }
        return name;
    }
    
    
    public String display() {
        StringBuilder sb = new StringBuilder();
        
        for(Map.Entry<String, ArrayList<String>> entry :this.entries.entrySet()){
            sb.append(entry.getKey());
            sb.append(": ");
            
            for(String pn : entry.getValue()){
                sb.append(pn);
                //sb.append(" ");
            }

        }
        
        return sb.toString();
    }
   
    
    
}