JDK 9 RFR(s): 8155052: add notes and links to j.u.Observer/Observable deprecation comments

[Stuart Marks]

Hi all,

Please review this small, non-normative textual change to j.u.Observable. This 
class, and its companion Observer interface, were deprecated earlier in JDK 9. 
Doug Lea suggested adding a link to j.u.c.Flow in case people confused these 
APIs with reactive streams. (AFAICS reactive streams doesn't use the terms 
observer/observable, but RxJava does.)

Thanks,

s'marks

# HG changeset patch
# User smarks
# Date 1490835538 25200
#      Wed Mar 29 17:58:58 2017 -0700
# Node ID 7b9ea7fa93c00698325d38cfc108cd6e79bffe10
# Parent  6b43c4698752779793d58813f46d3687c17dde75
8155052: add notes and links to j.u.Observer/Observable deprecation comments
Reviewed-by: XXX

diff -r 6b43c4698752 -r 7b9ea7fa93c0 
src/java.base/share/classes/java/util/Observable.java
--- a/src/java.base/share/classes/java/util/Observable.java	Tue Mar 28 18:12:38 
2017 -0700
+++ b/src/java.base/share/classes/java/util/Observable.java	Wed Mar 29 17:58:58 
2017 -0700
@@ -69,6 +69,8 @@
   * {@link java.beans} package.  For reliable and ordered
   * messaging among threads, consider using one of the concurrent data
   * structures in the {@link java.util.concurrent} package.
+ * For reactive streams style programming, see the
+ * {@link java.util.concurrent.Flow} API.
   */
  @Deprecated(since="9")
  public class Observable {