8252807: The jdk.jfr.Recording.getStream does not work when toDisk is disabled

Reviewed-by: mgronlun

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/Recording.java

@@ -577,6 +577,9 @@ public void setToDisk(boolean disk) {
      * Creates a data stream for a specified interval.
      * <p>
      * The stream may contain some data outside the specified range.
+     * <p>
+     * If the recording is not to disk, a stream can't be created
+     * and {@code null} is returned.
      *
      * @param start the start time for the stream, or {@code null} to get data from
      *        start time of the recording
@@ -585,12 +588,14 @@ public void setToDisk(boolean disk) {
      *        present time.
      *
      * @return an input stream, or {@code null} if no data is available in the
-     *         interval.
+     *         interval, or the recording was not recorded to disk
      *
      * @throws IllegalArgumentException if {@code end} happens before
      *         {@code start}
      *
      * @throws IOException if a stream can't be opened
+     *
+     * @see #setToDisk(boolean)
      */
     public InputStream getStream(Instant start, Instant end) throws IOException {
         if (start != null && end != null && end.isBefore(start)) {