title: How do i generate a unique id using UUID() which starts with an alphabet
body: <p>I have to generate a unique ID for a user name which contains the following reg-ex</p>
  
  <pre><code>^[a-zA-Z][a-zA-Z0-9.\\-_]{3,19}
  </code></pre>
  
  <p>I have to use the UUID() to generate the string and I have made the username 6 characters in length. I am trying to replace the first character with alphabet, its not working. The code I have written is :</p>
  
  <pre><code>String unique = UUID.randomUUID().toString();
  String name = unique.substring(30);
  String username = name.replaceFirst("[a-z]{0}", name));
  </code></pre>