[NO ISSUE][HYR] Add FunctionalInterface annotation

Change-Id: I7cdc0ac896ef9e856742e86eabcf77edf490e469
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/4383
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/ComputingAction.java b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/ComputingAction.java
index 147e871..1c9da52 100644
--- a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/ComputingAction.java
+++ b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/ComputingAction.java
@@ -18,6 +18,7 @@
  */
 package org.apache.hyracks.util;
 
+@FunctionalInterface
 public interface ComputingAction<T> {
     @SuppressWarnings("squid:S00112")
     T compute() throws Throwable;