title: ServletRequest.getParameterMap() returns Map<String, String[]> and ServletRequest.getParameter() returns String?
body: <p>Can someone explain to me why <code>ServletRequest.getParameterMap()</code> returns type </p>
  
  <pre><code>Map&lt;String, String[]&gt; 
  </code></pre>
  
  <p><code>ServletRequest.getParameter()</code> just returns type <code>String</code></p>
  
  <p>I'm don't understand why the map would ever map to more then one value. TIA.</p>