title: Do I need to check isDisposed() before calling dispose()?
body: <p>I'm learning RxJava and I noticed a lot of the sample code does a <code>isDisposed()</code> check before calling <code>dispose()</code>. I did not notice any issues when I called <code>dispose()</code> on an already disposed <code>Disposable</code>. </p>
  
  <p>So my question is, do I need the <code>isDisposed()</code> check? Are there situations where I should check <code>isDisposed()</code> before disposing? What are the pros and cons on doing the check first?</p>