Add a note about Guava version conflicts in cloud client library. (#1221)

* Add a note about Guava version conflicts in cloud client library.

* Make the note more general about Guava version conficts.

* Fix a typo

1 files changed, 12 insertions, 0 deletions

diff --git a/exporters/stats/stackdriver/README.md b/exporters/stats/stackdriver/README.md
index a10d9217..bda95e52 100644
--- a/exporters/stats/stackdriver/README.md
+++ b/exporters/stats/stackdriver/README.md
@@ -157,4 +157,16 @@ Stackdriver exporter adds a new `Metric` label for each custom `Metric` to ensur
 of the `Timeseries`. The format of the label is: `{LANGUAGE}-{PID}@{HOSTNAME}`, if `{PID}` is not
 available a random number will be used.
 
+### Why did I get an error "java.lang.NoSuchMethodError: com.google.common...", like "java.lang.NoSuchMethodError:com.google.common.base.Throwables.throwIfInstanceOf"?
+This is probably because there is a version conflict on Guava in the dependency tree.
+
+For example, `com.google.common.base.Throwables.throwIfInstanceOf` is introduced to Guava 20.0.
+If your application has a dependency that bundles a Guava with version 19.0 or below
+(for example, gRPC 1.10.0), it might cause a `NoSuchMethodError` since
+`com.google.common.base.Throwables.throwIfInstanceOf` doesn't exist before Guava 20.0.
+
+In this case, please either add an explicit dependency on a newer version of Guava that has the 
+new method (20.0 in the previous example), or if possible, upgrade the dependency that depends on 
+Guava to a newer version that depends on the newer Guava (for example, upgrade to gRPC 1.12.0).
+
 [stackdriver-monitoring]: https://cloud.google.com/monitoring/