diff --git a/src/controlP5/CDrawable.java b/src/controlP5/CDrawable.java
index 9fbe46a..ef52aeb 100755
--- a/src/controlP5/CDrawable.java
+++ b/src/controlP5/CDrawable.java
@@ -1,5 +1,3 @@
-package controlP5;
-
 /**
  * controlP5 is a processing gui library.
  *
@@ -25,12 +23,14 @@ package controlP5;
  *
  */
 
+package controlP5;
+
 import processing.core.PGraphics;
 
 /**
  * The CDrawable interface is used to draw controllers, primarily for internal use.
  */
-public interface CDrawable {
+@FunctionalInterface public interface CDrawable {
 
 	public void draw( PGraphics theGraphics );
 	
diff --git a/src/controlP5/CallbackListener.java b/src/controlP5/CallbackListener.java
index f1399ef..e2eb645 100755
--- a/src/controlP5/CallbackListener.java
+++ b/src/controlP5/CallbackListener.java
@@ -34,7 +34,7 @@ package controlP5;
  * @example use/ControlP5callback
  * @see controlP5.ControlP5#addCallback(CallbackListener)
  */
-public interface CallbackListener {
+@FunctionalInterface public interface CallbackListener {
 
 	public void controlEvent( CallbackEvent theEvent );
 
diff --git a/src/controlP5/ControlKey.java b/src/controlP5/ControlKey.java
index 81f930e..409b459 100755
--- a/src/controlP5/ControlKey.java
+++ b/src/controlP5/ControlKey.java
@@ -25,7 +25,8 @@ package controlP5;
  * 
  */
 
-public interface ControlKey {
+@FunctionalInterface public interface ControlKey {
 
 	public void keyEvent();
+
 }
diff --git a/src/controlP5/ControlListener.java b/src/controlP5/ControlListener.java
index ffc622e..df12ef1 100755
--- a/src/controlP5/ControlListener.java
+++ b/src/controlP5/ControlListener.java
@@ -34,7 +34,7 @@ package controlP5;
  * 
  * @example use/ControlP5listenerForSingleController
  */
-public interface ControlListener {
+@FunctionalInterface public interface ControlListener {
 
 	/**
 	 * controlEvent is called by controlP5's ControlBroadcaster to inform available listeners about
diff --git a/src/controlP5/ControllerInterface.java b/src/controlP5/ControllerInterface.java
index 6a4a355..033aee8 100755
--- a/src/controlP5/ControllerInterface.java
+++ b/src/controlP5/ControllerInterface.java
@@ -1,5 +1,3 @@
-package controlP5;
-
 /**
  * controlP5 is a processing gui library.
  * 
@@ -25,6 +23,8 @@ package controlP5;
  * 
  */
 
+package controlP5;
+
 import processing.core.PApplet;
 import processing.core.PFont;
 import processing.core.PGraphics;
@@ -35,7 +35,7 @@ import processing.event.KeyEvent;
  * The ControllerInterface is inherited by all ControllerGroup and Controller classes.
  * 
  */
-public interface ControllerInterface< T > {
+public interface ControllerInterface< T extends ControllerInterface< T > > {
 
 	@ControlP5.Invisible public void init( );
 
diff --git a/src/controlP5/ControllerView.java b/src/controlP5/ControllerView.java
index ca0f9d7..09e40f9 100755
--- a/src/controlP5/ControllerView.java
+++ b/src/controlP5/ControllerView.java
@@ -1,5 +1,3 @@
-package controlP5;
-
 /**
  * controlP5 is a processing gui library.
  * 
@@ -25,6 +23,8 @@ package controlP5;
  * 
  */
 
+package controlP5;
+
 import processing.core.PGraphics;
 
 /**
@@ -35,7 +35,7 @@ import processing.core.PGraphics;
  * 
  * @example use/ControlP5customDisplay
  */
-public interface ControllerView< T > {
+@FunctionalInterface public interface ControllerView< T extends ControllerView< T > > {
 
 	/**
 	 * draws your custom controllers. display() will be called by a controller's draw() function and