title: Appending a byte[] to the end of another byte[]
body: <p>I have two <code>byte[]</code> arrays which are of unknown length and I simply want to append one to the end of the other, i.e.:</p>
  
  <pre><code>byte[] ciphertext = blah;
  byte[] mac = blah;
  byte[] out = ciphertext + mac;
  </code></pre>
  
  <p>I have tried using <code>arraycopy()</code> but can't seem to get it to work.</p>