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Java Java Data Structures Efficiency! Using a Map to store Contact Methods

Did not get this part of the code

Please can you help me fix this part of the code, I really don't understand what he is trying to say

return what and how ?

package com.example.model;

import java.util.Map;
import java.util.Set;
import java.util.HashMap;

public class Contact {
  private String mFirstName;
  private String mLastName;
  private Map<String, String> mContactMethods;

  public Contact(String firstName, String lastName) {
    mFirstName = firstName;
    mLastName = lastName;
    /* This stores contact methods by name
     * eg:  "phone" => "(555) 555-1234"
    mContactMethods = new HashMap<String, String>();

  public void addContactMethod(String method, String value) {

    // TODO: Add to the contact method map

   * Returns the available contact methods.  eg: phone, pager,
   * @return The name of the contact methods that are available
  public Set<String> getAvailableContactMethods() {
    // FIXME: This should return the current contact method names.

    Set<String> CurrentContactMethods = mContactMethods.get(method);
    return  CurrentContactMethods;

   * Returns the value for the contact method if it exists, 
   * @param methodName  The name of the contact method to look up.
   * @return The name of the contact methods that are available
  public String getContactInfo(String methodName) {
    // FIXME: return the value for the passed in *methodName*
    return null;

  public String getFirstName() {
    return mFirstName;

  public String getLastName() {
    return mLastName;


1 Answer

Hi there,

The hint in the question suggests you want to return a set of the keys within the mContactMethods map. You can use the method keySet() to do that. So, return the result of calling keySet() on mContactMethods using dot notation.

Make sense?


Thanks , It kind of slipped off my mind. Appreciate your reply.