title: Lambda expression with Double Comparator
body: <p>How can I convert this expression:<code>(i1,i2) -&gt; (int) i1 - (int) i2</code>
  from int to double values.</p>
  <p>I tried this:<code>(i1,i2) -&gt; (double) i1 - (double) i2</code>, it's wrong.</p>
  <p>Please help. Thanks.</p>