title: Char Array vs String: which is better for storing a set of letters
body: <p>I need to store in a constant class 4 letter of a code. I can do:</p>
  
  <pre><code>static final String CODE_LETTERS = "TRWAG";
  </code></pre>
  
  <p>or</p>
  
  <pre><code>static final char[] CODE_LETTERS = {'T', 'R', 'W', 'A', 'G'};
  </code></pre>
  
  <p>After, I can obtain one of that characters in two ways:</p>
  
  <pre><code>final char codeLetter = CODE_LETTERS.charAt(index);
  </code></pre>
  
  <p>or</p>
  
  <pre><code>final char codeLetter = CODE_LETTERS[index];
  </code></pre>
  
  <p>what is the best way?. Please take in mind correction, performance, etc.</p>