title: Count occurrences by stream
body: <pre><code>LinkedList&lt;Double&gt; list = new LinkedList&lt;Double&gt;();
  list.add(9.5);
  list.add(4.9);
  list.add(3.2);
  list.add(4.9);
  </code></pre>
  
  <p>I want to count the duplicate element in the list through a stream and put them into a <code>HashMap</code>  which represent the occurrence of each number in the list:
  e.g: (9.5=1, 4.9=2, 3.2=1)
  Does anybody know how this works?</p>