title: HashMap value auto increment
body: <p>when I was coding, one question occurred to me, <strong>which is if the value part(Integer) in the HashMap is able to auto-increment in the following scenario?</strong></p>
  
  <pre><code>Map&lt;String, Integer&gt; dictionary = new HashMap&lt;String, Integer&gt;();    
  dictionary.put("a",1);
  dictionary.put("b",1);
  </code></pre>