src/share/classes/java/util/stream/Stream.java
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rev 7573 : 8015315: Stream.concat methods
Contributed-by: brian.goetz@oracle.com, henry.jen@oracle.com
*** 881,886 ****
--- 881,911 ----
public static<T> Stream<T> generate(Supplier<T> s) {
Objects.requireNonNull(s);
return StreamSupport.stream(
new StreamSpliterators.InfiniteSupplyingSpliterator.OfRef<>(Long.MAX_VALUE, s));
}
+
+ /**
+ * Creates a lazy concatenated {@code Stream} whose elements are all the
+ * elements of a first {@code Stream} succeeded by all the elements of the
+ * second {@code Stream}. The resulting stream is ordered if both
+ * of the input streams are ordered, and parallel if either of the input
+ * streams is parallel.
+ *
+ * @param <T> The type of stream elements
+ * @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 input streams
+ */
+ public static <T> Stream<T> concat(Stream<? extends T> a, Stream<? extends T> b) {
+ Objects.requireNonNull(a);
+ Objects.requireNonNull(b);
+
+ @SuppressWarnings("unchecked")
+ Spliterator<T> split = new Streams.ConcatSpliterator.OfRef<>(
+ (Spliterator<T>) a.spliterator(), (Spliterator<T>) b.spliterator());
+ return (a.isParallel() || b.isParallel())
+ ? StreamSupport.parallelStream(split)
+ : StreamSupport.stream(split);
+ }
}