title: Store the values without overwriting
body: <p>I have a <code>Map&lt;String, Integer&gt;</code> e.g.</p>
  
  <ol>
  <li><code>"aaa", 1</code></li>
  <li><code>"bbb", 2</code></li>
  <li><code>"ccc", 3</code></li>
  <li><code>"aaa", 4</code></li>
  </ol>
  
  <p>The problem is that the <code>HashMap</code> does not store all key and values, as I've understood, when i try add the last pair <code>("aaa", 4)</code>, it will not be added, instead of this, the value for <code>"aaa"</code> (I mean 1) will be overwritten on 4.</p>
  
  <p>I know, that I could create class, where I could store these pairs, but I need another solution. (without creating a new class)</p>
  
  <p>EDIT ------------------------------------
  Actually I have much more pairs, and I do not have uniques String or Integers, I mean that, if even I have two similar pairs  they will be stored</p>