title: Why is there no function Stream.flatMap()?
body: <p>Why is there no function <code>Stream.flatMap()</code> (without any parameters) to flatten a <code>Stream&lt;Stream&lt;T&gt;&gt;</code>?</p>
  
  <p>It would simply be implemented as <code>Stream.flatMap(o -&gt; o)</code>.</p>
  
  <p>In my opinion, this is by far the most common use of <a href="https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#flatMap-java.util.function.Function-" rel="noreferrer">flatMap(Function mapper)</a>.</p>