title: Ignore duplicates when producing map using streams
body: <pre><code>Map&lt;String, String&gt; phoneBook = people.stream()
                                        .collect(toMap(Person::getName,
                                                       Person::getAddress));
  </code></pre>
  
  <p>I get <code>java.lang.IllegalStateException: Duplicate key</code> when a duplicated element is found. </p>
  
  <p>Is it possible to ignore such exception on adding values to the map?</p>
  
  <p>When there is duplicate it simply should continue by ignoring that duplicate key.</p>