title: Trouble using isDigit()
body: <p>I am trying to use isDigit() to verify if a character in a string is not a digit.</p>
  
  <pre><code>if (aString.charAt(i).isDigit == false)
  </code></pre>
  
  <p>I am getting the error: cannot invoke isDigit on the primitive type character. What am I doing wrong?</p>