diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action.java
index 09c45da9a6..0640931b13 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action {
     void invoke();
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action1.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action1.java
index 6cd1fd7230..fd4c0c3ef9 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action1.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action1.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action1<T1> {
     void invoke(T1 param1);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action2.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action2.java
index 6f4d74080c..c29b7fb77b 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action2.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action2.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action2<T1, T2> {
     void invoke(T1 param1, T2 param2);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action3.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action3.java
index 3743dae08c..12d3681083 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action3.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action3.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action3<T1, T2, T3> {
     void invoke(T1 param1, T2 param2, T3 param3);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action4.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action4.java
index 918e9c7568..d02a190983 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action4.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action4.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action4<T1, T2, T3, T4> {
     void invoke(T1 param1, T2 param2, T3 param3, T4 param4);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action5.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action5.java
index 8f73f053de..967e896e74 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action5.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action5.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action5<T1, T2, T3, T4, T5> {
     void invoke(T1 param1, T2 param2, T3 param3, T4 param4, T5 param5);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action6.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action6.java
index 54185b4040..803712c510 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action6.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action6.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action6<T1, T2, T3, T4, T5, T6> {
     void invoke(T1 param1, T2 param2, T3 param3, T4 param4, T5 param5, T6 param6);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action7.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action7.java
index 8484ca3a0e..08a9880ff1 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action7.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action7.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action7<T1, T2, T3, T4, T5, T6, T7> {
     void invoke(T1 param1, T2 param2, T3 param3, T4 param4, T5 param5, T6 param6, T7 param7);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action8.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action8.java
index 700f4933d8..9b573930bc 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action8.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/Action8.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface Action8<T1, T2, T3, T4, T5, T6, T7, T8> {
     void invoke(T1 param1, T2 param2, T3 param3, T4 param4, T5 param5, T6 param6, T7 param7, T8 param8);
 }
diff --git a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/ActionBase.java b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/ActionBase.java
index bb95ca6515..6e1d04ef25 100644
--- a/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/ActionBase.java
+++ b/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/ActionBase.java
@@ -3,6 +3,7 @@
 
 package com.microsoft.aspnet.signalr;
 
+@FunctionalInterface
 public interface ActionBase {
     void invoke(Object ... params);
 }