title: Looking for a Regex for only a certain type of chars and no duplication
body: <p>I am looking for a regex only for certain chars and no duplications. I have to write an app for a restaurant and they want to write the allergens of the food (ABCDEFGHLMNOPR). Therefore only those chars should be allowed without duplications. </p>
  
  <p>I am using primefaces and I tried a lot of different regex before. They worked on <a href="https://regex101.com/r/dVohnx/1" rel="nofollow noreferrer">https://regex101.com/r/dVohnx/1</a> but sadly not in the app.</p>
  
  <p>//this regEx works on regex101 online editor but not for me.</p>
  
  <pre><code>&lt;p:inputText id="id" value="#{allergene}" disabled="#{!speiseplanView.editable and hasEditPermission}"&gt;
     &lt;p:keyFilter regEx="/^(?:([ABCDEFGHLMNOPR])(?!\1))+$/" /&gt;
  &lt;/p:inputText&gt;
  </code></pre>
  
  <p>The problem is, I only limited the chars with that code but not the duplication. </p>
  
  <p>thank you, guys!</p>