title: What is the meaning of a dollar sign before an Android resource id
body: <p>In the accepted answer of the following post(<a href="https://stackoverflow.com/questions/21872150/android-custom-numeric-keyboard/21873135">Android custom numeric keyboard</a>) I found a syntax that I don't understand: </p>
  
  <pre><code>$(R.id.t9_key_0).setOnClickListener(this);
  </code></pre>
  
  <p>What does the dollar sign mean in front? Is it specifically related to Android resource ids or is more a general Java syntax? Search engine results didn't show any suitable results. </p>