title: java Get hashmap keys as integer array
body: <p>I have a hashmap like this</p>
  
  <pre><code>public HashMap &lt;String,People&gt; valueHashMap  = new Hashmap();
  </code></pre>
  
  <p>Here the key to my HashMap is time in seconds as string, ie I am adding value to hashmap like this</p>
  
  <pre><code>long timeSinceEpoch = System.currentTimeMillis()/1000;
  valueHashMap.put(
                     Integer.toString((int)timeSinceEpoch)
                     , people_obj
                  );
  </code></pre>
  
  <p>Now I want to get all keys in the hashmap into an array list of integer.</p>
  
  <pre><code>ArrayList&lt;Integer&gt; intKeys = valueHashMap.keys()...
  </code></pre>
  
  <p>Is there any way to do that?</p>