title: Java: what is 1d?
body: <p>Came across the following expression on Java and I have no idea what "1d" means (<code>r</code> is an integer). There are also <a href="https://stackoverflow.com/questions/15701795/1l-for-long-1f-for-float-1d-for-double-what-about-byte">options</a> for longs, doubles... What are they and what are they used for? </p>
  
  <pre><code>double y = r / (Integer.MAX_VALUE + 1d);
  </code></pre>
  
  <p>Thanks!</p>