SPIGOT-2540: Add nullability annotations to entire Bukkit API

By: Darkyenus <darkyenus@gmail.com>

paper-api/src/main/java/org/bukkit/event/hanging/HangingBreakByEntityEvent.java

@@ -2,6 +2,8 @@ package org.bukkit.event.hanging;
 
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.Hanging;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * Triggered when a hanging entity is removed by an entity
@@ -9,20 +11,22 @@ import org.bukkit.entity.Hanging;
 public class HangingBreakByEntityEvent extends HangingBreakEvent {
     private final Entity remover;
 
-    public HangingBreakByEntityEvent(final Hanging hanging, final Entity remover) {
+    public HangingBreakByEntityEvent(@NotNull final Hanging hanging, @Nullable final Entity remover) {
         this(hanging, remover, HangingBreakEvent.RemoveCause.ENTITY);
     }
 
-    public HangingBreakByEntityEvent(final Hanging hanging, final Entity remover, final HangingBreakEvent.RemoveCause cause) {
+    public HangingBreakByEntityEvent(@NotNull final Hanging hanging, @Nullable final Entity remover, @NotNull final HangingBreakEvent.RemoveCause cause) {
         super(hanging, cause);
         this.remover = remover;
     }
 
     /**
-     * Gets the entity that removed the hanging entity
+     * Gets the entity that removed the hanging entity.
+     * May be null, for example when broken by an explosion.
      *
      * @return the entity that removed the hanging entity
      */
+    @Nullable
     public Entity getRemover() {
         return remover;
     }

paper-api/src/main/java/org/bukkit/event/hanging/HangingBreakEvent.java

@@ -3,6 +3,7 @@ package org.bukkit.event.hanging;
 import org.bukkit.entity.Hanging;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Triggered when a hanging entity is removed
@@ -12,7 +13,7 @@ public class HangingBreakEvent extends HangingEvent implements Cancellable {
     private boolean cancelled;
     private final HangingBreakEvent.RemoveCause cause;
 
-    public HangingBreakEvent(final Hanging hanging, final HangingBreakEvent.RemoveCause cause) {
+    public HangingBreakEvent(@NotNull final Hanging hanging, @NotNull final HangingBreakEvent.RemoveCause cause) {
         super(hanging);
         this.cause = cause;
     }
@@ -22,6 +23,7 @@ public class HangingBreakEvent extends HangingEvent implements Cancellable {
      *
      * @return the RemoveCause for the hanging entity's removal
      */
+    @NotNull
     public HangingBreakEvent.RemoveCause getCause() {
         return cause;
     }
@@ -60,11 +62,13 @@ public class HangingBreakEvent extends HangingEvent implements Cancellable {
         DEFAULT,
     }
 
+    @NotNull
     @Override
     public HandlerList getHandlers() {
         return handlers;
     }
 
+    @NotNull
     public static HandlerList getHandlerList() {
         return handlers;
     }

paper-api/src/main/java/org/bukkit/event/hanging/HangingEvent.java

@@ -2,6 +2,7 @@ package org.bukkit.event.hanging;
 
 import org.bukkit.entity.Hanging;
 import org.bukkit.event.Event;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * Represents a hanging entity-related event.
@@ -9,7 +10,7 @@ import org.bukkit.event.Event;
 public abstract class HangingEvent extends Event {
     protected Hanging hanging;
 
-    protected HangingEvent(final Hanging painting) {
+    protected HangingEvent(@NotNull final Hanging painting) {
         this.hanging = painting;
     }
 
@@ -18,6 +19,7 @@ public abstract class HangingEvent extends Event {
      *
      * @return the hanging entity
      */
+    @NotNull
     public Hanging getEntity() {
         return hanging;
     }

paper-api/src/main/java/org/bukkit/event/hanging/HangingPlaceEvent.java

@@ -6,6 +6,8 @@ import org.bukkit.entity.Hanging;
 import org.bukkit.entity.Player;
 import org.bukkit.event.Cancellable;
 import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * Triggered when a hanging entity is created in the world
@@ -17,7 +19,7 @@ public class HangingPlaceEvent extends HangingEvent implements Cancellable {
     private final Block block;
     private final BlockFace blockFace;
 
-    public HangingPlaceEvent(final Hanging hanging, final Player player, final Block block, final BlockFace blockFace) {
+    public HangingPlaceEvent(@NotNull final Hanging hanging, @Nullable final Player player, @NotNull final Block block, @NotNull final BlockFace blockFace) {
         super(hanging);
         this.player = player;
         this.block = block;
@@ -29,6 +31,7 @@ public class HangingPlaceEvent extends HangingEvent implements Cancellable {
      *
      * @return the player placing the hanging entity
      */
+    @Nullable
     public Player getPlayer() {
         return player;
     }
@@ -38,6 +41,7 @@ public class HangingPlaceEvent extends HangingEvent implements Cancellable {
      *
      * @return the block that the hanging entity was placed on
      */
+    @NotNull
     public Block getBlock() {
         return block;
     }
@@ -47,6 +51,7 @@ public class HangingPlaceEvent extends HangingEvent implements Cancellable {
      *
      * @return the face of the block that the hanging entity was placed on
      */
+    @NotNull
     public BlockFace getBlockFace() {
         return blockFace;
     }
@@ -59,11 +64,13 @@ public class HangingPlaceEvent extends HangingEvent implements Cancellable {
         this.cancelled = cancel;
     }
 
+    @NotNull
     @Override
     public HandlerList getHandlers() {
         return handlers;
     }
 
+    @NotNull
     public static HandlerList getHandlerList() {
         return handlers;
     }