Functional interfaces should be annotated as functional interfaces

Mage/src/main/java/mage/MageItem.java

@@ -35,6 +35,7 @@ import java.util.UUID;
  *
  * @author BetaSteward_at_googlemail.com
  */
+@FunctionalInterface
 public interface MageItem extends Serializable {
 
     UUID getId();

Mage/src/main/java/mage/abilities/condition/Condition.java

@@ -10,6 +10,7 @@ import mage.game.Game;
  *
  * @author nantuko, noxx
  */
+@FunctionalInterface
 public interface Condition extends Serializable {
 
     public enum ComparisonType {

Mage/src/main/java/mage/abilities/costs/AdjustingSourceCosts.java

@@ -1,3 +1,4 @@
+/*
 /*
  *  Copyright 2010 BetaSteward_at_googlemail.com. All rights reserved.
  *
@@ -38,6 +39,7 @@ import mage.game.Game;
  *
  * @author nantuko
  */
+@FunctionalInterface
 public interface AdjustingSourceCosts {
     void adjustCosts(Ability ability, Game game);
 }

Mage/src/main/java/mage/abilities/costs/mana/AlternateManaPaymentAbility.java

@@ -38,6 +38,7 @@ import mage.game.Game;
  *
  * @author LevelX2
  */
+@FunctionalInterface
 public interface AlternateManaPaymentAbility {
     /**
      * Adds the special action to the state, that allows the user to do the alternate mana payment

Mage/src/main/java/mage/abilities/mana/builder/Builder.java

@@ -32,6 +32,7 @@ import java.io.Serializable;
 /**
  * @author noxx
  */
+@FunctionalInterface
 public interface Builder<T> extends Serializable {
 
     T build(Object... options);

Mage/src/main/java/mage/filter/predicate/ObjectPlayerPredicate.java

@@ -32,5 +32,6 @@ package mage.filter.predicate;
  * @author North
  * @param <T>
  */
+@FunctionalInterface
 public interface ObjectPlayerPredicate<T extends ObjectPlayer> extends Predicate<T> {
 }

Mage/src/main/java/mage/filter/predicate/ObjectSourcePlayerPredicate.java

@@ -32,5 +32,6 @@ package mage.filter.predicate;
  * @author North
  * @param <T>
  */
+@FunctionalInterface
 public interface ObjectSourcePlayerPredicate<T extends ObjectSourcePlayer> extends ObjectPlayerPredicate<T> {
 }

Mage/src/main/java/mage/filter/predicate/Predicate.java

@@ -36,6 +36,7 @@ import mage.game.Game;
  * @author North
  * @param <T>
  */
+@FunctionalInterface
 public interface Predicate <T> extends Serializable {
     /**
      * Returns the result of applying this predicate to {@code input}. This method is <i>generally

Mage/src/main/java/mage/game/Table.java

@@ -64,6 +64,7 @@ public class Table implements Serializable {
     private Tournament tournament;
     private TableRecorder recorder;
 
+    @FunctionalInterface
     public interface TableRecorder {
         void record(Table table);
     }

Mage/src/main/java/mage/game/events/Listener.java

@@ -34,6 +34,7 @@ import java.io.Serializable;
  *
  * @author BetaSteward_at_googlemail.com
  */
+@FunctionalInterface
 public interface Listener<E extends ExternalEvent> extends Serializable {
     void event(E event);
 }

Mage/src/main/java/mage/util/CircularList.java

@@ -27,6 +27,8 @@
  */
 package mage.util;
 
+
+
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collection;

Mage/src/main/java/mage/util/Copyable.java

@@ -32,7 +32,7 @@ package mage.util;
  *
  * @author BetaSteward_at_googlemail.com
  */
+@FunctionalInterface
 public interface Copyable<T> {
-
     T copy();
 }

Mage/src/main/java/mage/util/functions/Function.java

@@ -30,6 +30,7 @@ package mage.util.functions;
 /**
  * @author nantuko
  */
+@FunctionalInterface
 public interface Function<X, Y> {
     X apply(Y in);
 }