title: How to match stream elements but return false if non exists?
body: <p>I have a stream and would like to check if all match a filter. If all match, return <code>true</code>.</p>
  
  <p>But, if the stream is empty, I'd like to return <code>false</code>.</p>
  
  <p>How can I do this?</p>
  
  <p>Example code:</p>
  
  <pre><code>public boolean validate(Stream&lt;Whatever&gt; stream) {
    // Problem: returns **true** if stream empty.
    // How can **false** be returned if stream is empty?
    return stream.allMatch(Whatever::someCheck);
  }
  </code></pre>