[B+C] Add and implement an EntityDespawnEvent. adds BUKKIT-5645

src/main/java/org/bukkit/event/entity/EntityDespawnEvent.java

@@ -0,0 +1,63 @@
+package org.bukkit.event.entity;
+
+import org.bukkit.entity.Entity;
+import org.bukkit.event.HandlerList;
+
+/**
+ * Called whenever an Entity is removed from the world.
+ */
+public class EntityDespawnEvent extends EntityEvent {
+    /**
+     * An enum to specify the type of despawning
+     */
+    public enum DespawnReason {
+        /**
+         * When an entity despawns due to a chunk unload
+         */
+        CHUNK_UNLOAD,
+        /**
+         * When a living entity despawns because it died
+         */
+        DEATH,
+        /**
+         * When an entity despawns because a plugin or GameRule removed it,
+         * or a non-living entity died (EG, ender crystal destroyed)
+         */
+        REMOVED,
+        /**
+         * When an entity is missing a DespawnReason
+         */
+        DEFAULT
+    }
+
+    private static final HandlerList handlers = new HandlerList();
+    private final DespawnReason despawnReason;
+
+    public EntityDespawnEvent(final Entity entity) {
+        super(entity);
+        despawnReason = DespawnReason.DEFAULT;
+    }
+
+    public EntityDespawnEvent(final Entity entity, DespawnReason reason) {
+        super(entity);
+        despawnReason = reason;
+    }
+
+    /**
+     * Gets the reason for why the entity is being despawned.
+     *
+     * @return The {@link DespawnReason} detailing the reason for the entity being despawned
+     */
+    public DespawnReason getDespawnReason() {
+        return despawnReason;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}