title: Throw exception if Optional<> value is present
body: <p>Suppose I have a Spring Data Repository method.</p>
  
  <pre><code>Optional&lt;Branch&gt; findByName(@Nonnull final String name);
  </code></pre>
  
  <p>My business logic is such if I find any value for this method execution  I would throw an exception.</p>
  
  <p>I could do this  for example :</p>
  
  <pre><code>Optional.of(branchRepository.findByName(branch.getName()))
                  .filter(bo -&gt; !bo.isPresent())
                  .orElseThrow(NameNotAvailableException::new);
  </code></pre>
  
  <p>or another way: </p>
  
  <pre><code>Optional.of(branchRepository.findByName(branch.getName()))
                  .filter(Optional::isEmpty)
                  .orElseThrow(NameNotAvailableException::new);
  </code></pre>
  
  <p>I am not sure if using filter, in this case, is appropriate as my method returns <code>Optional&lt;Branch&gt;</code> 
  not a list. 
  It seems that if in JDK if there were ifPresentThrow() method was available that would serve my purpose. </p>
  
  <p><strong>Yes, this code can be written in an imperative style which I don't want. So my question is the same kind of things ifPresentThrow() can be achieved or there is a better way to do it in a functional style. Thanks in advance.</strong></p>