Split only 3 letter StringBuilder
<p>My <code>StringBuilder</code>:</p>

<pre><code>StringBuilder s = new StringBuilder();
</code></pre>

<p>And the output:</p>

<pre><code>s.toString() = "ABCDEFG"
</code></pre>

<p>I just want the 3 letters of the beginning. Like "<code>ABC</code>".
What code do I need to use to do this?</p>
