title: Custom RegEx for Username/Email Address Java
body: <p>Somehow I find it really hard to create a RegEx on my own and I am sure one of you does know how to work with them. My question: I want users, who register, to only be able to enter an email address of this format: <code>?.????@example.com</code>. </p>
  
  <p>To clear up, my RegEx should look for if there is only one character in the first position, followed by a dot, an infinite number of characters, an at-symbol, followed by "example.com".</p>
  
  <p>Is it even possible to allow RegEx to look for full strings (<code>example.com</code> in this case) and if so, what would that RegEx look like? (I'd like an full example).</p>
  
  <p><strong>EDIT:</strong> By characters I mean alphanumeric characters (<code>^[a-zA-z]$</code>) </p>
  
  <p>Thanks in advance!</p>