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

how to return the available contacts.

In this task, let's fix the getAvailableContactMethods method. We want to return a set of the currently defined contact methods.

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) {
   mContactMethods.put(method,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.
    return mContactMethods;

   * 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

Rob Bridges
.a{fill-rule:evenodd;}techdegree seal-36
Rob Bridges
Full Stack JavaScript Techdegree Graduate 35,467 Points

Hey there admire,

Each map has a function built into it that will return each of the keys in the map.

So to return keys the method would return something like below.

return mapName.keySet();

changing mapName to be whatever the name of your map is that you want to return the keys of.

Thanks give me a shout if this doesn't help.