Set version number to 2.2.1 in trunk.
diff --git a/java/pom.xml b/java/pom.xml
index 91874e7..849ef5d 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -10,7 +10,7 @@
   </parent>
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-java</artifactId>
-  <version>2.2.0-pre</version>
+  <version>2.2.1-pre</version>
   <packaging>jar</packaging>
   <name>Protocol Buffer Java API</name>
   <description>