title: Extracting the initial characters from a string in one go
body: <p>please advise below is the code to extract the first 4 characters from the string as shown below..</p>
  
  <pre><code>String external = ak.getReference();    
  String s= external.substring(0,4);
  </code></pre>
  
  <p>Can I wrap this into one so that no extra String s need to be created and finally string external will have four initial characters in one go</p>