src/share/classes/java/util/stream/DoubleStream.java

rev 7532 : 8015315: Stream.concat methods
Contributed-by: brian.goetz@oracle.com, henry.jen@oracle.com

*** 744,749 ****
--- 744,771 ----
      public static DoubleStream generate(DoubleSupplier s) {
          Objects.requireNonNull(s);
          return StreamSupport.doubleStream(
                  new StreamSpliterators.InfiniteSupplyingSpliterator.OfDouble(Long.MAX_VALUE, s));
      }
+ 
+     /**
+      * Creates a lazy concatenated {@code DoubleStream} whose elements are all the
+      * elements of a first {@code DoubleStream} succeeded by all the elements of the
+      * second {@code DoubleStream}. The resulting stream is ordered if both
+      * of the input streams are ordered, and parallel if either of the input
+      * streams is parallel.
+      *
+      * @param a the first stream
+      * @param b the second stream to concatenate on to end of the first stream
+      * @return the concatenation of the two streams
+      */
+     public static DoubleStream concat(DoubleStream a, DoubleStream b) {
+         Objects.requireNonNull(a);
+         Objects.requireNonNull(b);
+ 
+         Spliterator.OfDouble split = new Streams.ConcatSpliterator.OfDouble(
+                 a.spliterator(), b.spliterator());
+         return (a.isParallel() || b.isParallel())
+                ? StreamSupport.doubleParallelStream(split)
+                : StreamSupport.doubleStream(split);
+     }
  }