chore: Remove Source#future in javadsl

Author: He-Pin

stream-tests/src/test/java/org/apache/pekko/stream/javadsl/LazyAndFutureSourcesTest.java

@@ -27,7 +27,6 @@
 import org.apache.pekko.testkit.PekkoSpec;
 import org.junit.ClassRule;
 import org.junit.Test;
-import scala.concurrent.Future;
 
 public class LazyAndFutureSourcesTest extends StreamTest {
 
@@ -41,14 +40,6 @@ public LazyAndFutureSourcesTest() {
 
   // note these are minimal happy path tests to cover API, more thorough tests are on the Scala side
 
-  @Test
-  public void future() throws Exception {
-    CompletionStage<List<String>> result =
-        Source.future(Future.successful("one")).runWith(Sink.seq(), system);
-
-    assertEquals(Arrays.asList("one"), result.toCompletableFuture().get(3, TimeUnit.SECONDS));
-  }
-
   @Test
   public void completionStage() throws Exception {
     CompletionStage<String> one = CompletableFuture.completedFuture("one");

stream/src/main/scala/org/apache/pekko/stream/javadsl/Source.scala

@@ -20,7 +20,7 @@ import java.util.concurrent.{ CompletableFuture, CompletionStage }
 import scala.annotation.{ nowarn, varargs }
 import scala.annotation.unchecked.uncheckedVariance
 import scala.collection.immutable
-import scala.concurrent.{ Future, Promise }
+import scala.concurrent.Promise
 import scala.concurrent.ExecutionContext
 import scala.jdk.CollectionConverters._
 import scala.jdk.DurationConverters._
@@ -311,15 +311,6 @@ object Source {
   def failed[T](cause: Throwable): Source[T, NotUsed] =
     new Source(scaladsl.Source.failed(cause))
 
-  /**
-   * Emits a single value when the given Scala `Future` is successfully completed and then completes the stream.
-   * The stream fails if the `Future` is completed with a failure.
-   *
-   * Here for Java interoperability, the normal use from Java should be [[Source.completionStage]]
-   */
-  def future[T](futureElement: Future[T]): Source[T, NotUsed] =
-    scaladsl.Source.future(futureElement).asJava
-
   /**
    * Never emits any elements, never completes and never fails.
    * This stream could be useful in tests.
@@ -332,7 +323,7 @@ object Source {
    * If the `CompletionStage` is completed with a failure the stream is failed.
    */
   def completionStage[T](completionStage: CompletionStage[T]): Source[T, NotUsed] =
-    future(completionStage.asScala)
+    new Source(scaladsl.Source.future(completionStage.asScala))
 
   /**
    * Turn a `CompletionStage[Source]` into a source that will emit the values of the source when the future completes successfully.