import java.io.*;
import java.util.Scanner;
import java.util.*;

public class ArrayListPD
 {

  // Data Fields 
  private List<DirectoryEntry> myDir  = new ArrayList<DirectoryEntry>();   //The array to contain the directory data 
  private boolean modified = false;

  /** Add an entry or change an existing entry.
    @param name The name of the person being added or changed
    @param number The new number to be assigned
    @return The old number or, if a new entry, null
   */
  public String addOrChangeEntry(String name, String newNumber) {    
    return "not implemented yet";
  }

  /** Look up an entry.
      @param name The name of the person
      @return The number. If not in the directory, null is returned
   */
  public String lookupEntry(String name) {
      return "not implemented yet";
  }


  /** Remove an entry from the directory.
          @param name The name of the person to be removed
          @return The current number. If not in directory, null is
          returned
   */
  public String removeEntry(String name) {
    return "not implemented yet";
  }  // end remove Entry
  
 
  /** Method to save the directory.
      pre:  The directory has been loaded with data.
      post: Contents of directory written back to the file in the
            form of name-number pairs on adjacent lines.
            modified is reset to false.
   */
  public void save() {
  } 
}