title: Collect HashSet / Java 8 / Regex Pattern / Stream API
body: <p>Recently I change version of the JDK 8 instead 7 of my project and now I overwrite some code snippets using new features that came with Java 8.</p>
  
  <pre><code>final Matcher mtr = Pattern.compile(regex).matcher(input);
  
  HashSet&lt;String&gt; set = new HashSet&lt;String&gt;() {{
      while (mtr.find()) add(mtr.group().toLowerCase());
  }};
  </code></pre>
  
  <p><strong>How I can write this code using Stream API ?</strong></p>