Add Source.fromJavaStream as convenient method alias (#28881)

akka-stream/src/main/scala/akka/stream/javadsl/Source.scala

@@ -100,6 +100,17 @@ object Source {
   def fromIterator[O](f: function.Creator[java.util.Iterator[O]]): javadsl.Source[O, NotUsed] =
     new Source(scaladsl.Source.fromIterator(() => f.create().asScala))
 
+  /**
+   * Creates a source that wraps a Java 8 ``Stream``. ``Source`` uses a stream iterator to get all its
+   * elements and send them downstream on demand.
+   *
+   * You can use [[Source.async]] to create asynchronous boundaries between synchronous java stream
+   * and the rest of flow.
+   */
+  def fromJavaStream[O, S <: java.util.stream.BaseStream[O, S]](
+      stream: function.Creator[java.util.stream.BaseStream[O, S]]): javadsl.Source[O, NotUsed] =
+    StreamConverters.fromJavaStream(stream)
+
   /**
    * Helper to create 'cycled' [[Source]] from iterator provider.
    * Example usage: