title: Java Comparator alphanumeric strings
body: <p>I want to implement my custom Comparator to sort a map of keys in this particular way:</p>
  
  <pre><code>1
  2
  3
  4
  4a
  4b
  5
  6
  11
  12
  12a
  ...
  </code></pre>
  
  <p>And I dont know how can do it exactly. I have impelemented this only for numeric values:</p>
  
  <pre><code>aaa = new TreeMap&lt;String, ArrayList&lt;ETrack&gt;&gt;(
      new Comparator&lt;String&gt;()
      {
        @Override
        public int compare(String s1, String s2)
        {
          return Integer.valueOf(s1).compareTo(Integer.valueOf(s2));
        }
      });
  </code></pre>
  
  <p>But this is not obiouslly the complete solution. Any idea?</p>