title: Understanding the $ in Java's format strings
body: <pre><code> StringBuilder sb = new StringBuilder();
   // Send all output to the Appendable object sb
   Formatter formatter = new Formatter(sb, Locale.US);
  
   // Explicit argument indices may be used to re-order output.
   formatter.format("%4$2s %3$2s %2$2s %1$2s", "a", "b", "c", "d")
   // -&gt; " d  c  b  a"
  </code></pre>
  
  <p>In this case, why is a 2 appended to $? </p>