Added new PlayerExpChangeEvent and PlayerLevelChangeEvent events. Thanks to feildmaster for the PR.

By: Nathan Adams <dinnerbone@dinnerbone.com>

paper-api/src/main/java/org/bukkit/event/Event.java

@@ -363,6 +363,18 @@ public abstract class Event implements Serializable {
          * @see org.bukkit.event.player.PlayerChangedWorldEvent
          */
         PLAYER_CHANGED_WORLD(Category.PLAYER, PlayerChangedWorldEvent.class),
+        /**
+         * Called when a players level changes
+         *
+         * @see org.bukkit.event.player.PlayerLevelChangeEvent
+         */
+        PLAYER_LEVEL_CHANGE(Category.PLAYER, PlayerLevelChangeEvent.class),
+        /**
+         * Called when a players experience changes naturally
+         *
+         * @see org.bukkit.event.player.PlayerExpChangeEvent
+         */
+        PLAYER_EXP_CHANGE(Category.PLAYER, PlayerExpChangeEvent.class),
 
         /**
          * BLOCK EVENTS

paper-api/src/main/java/org/bukkit/event/player/PlayerExpChangeEvent.java

@@ -0,0 +1,43 @@
+package org.bukkit.event.player;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.HandlerList;
+
+/**
+ * Called when a players experience changes naturally
+ */
+public class PlayerExpChangeEvent extends PlayerEvent {
+    private static final HandlerList handlers = new HandlerList();
+    private int exp;
+
+    public PlayerExpChangeEvent(Player player, int expAmount) {
+         super(Type.PLAYER_EXP_CHANGE, player);
+         exp = expAmount;
+    }
+
+    /**
+     * Get the amount of experience the player will receive
+     *
+     * @return The amount of experience
+     */
+    public int getAmount() {
+        return exp;
+    }
+
+    /**
+     * Set the amount of experience the player will receive
+     *
+     * @param amount The amount of experience to set
+     */
+    public void setAmount(int amount) {
+        exp = amount;
+    }
+
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

paper-api/src/main/java/org/bukkit/event/player/PlayerLevelChangeEvent.java

@@ -0,0 +1,45 @@
+package org.bukkit.event.player;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.HandlerList;
+
+/**
+ * Called when a players level changes
+ */
+public class PlayerLevelChangeEvent extends PlayerEvent {
+    private static final HandlerList handlers = new HandlerList();
+    private int oldLevel;
+    private int newLevel;
+
+    public PlayerLevelChangeEvent(Player player, int oldLevel, int newLevel) {
+         super(Type.PLAYER_LEVEL_CHANGE, player);
+         this.oldLevel = oldLevel;
+         this.newLevel = newLevel;
+    }
+
+    /**
+     * Gets the old level of the player
+     *
+     * @return The old level of the player
+     */
+    public int getOldLevel() {
+        return oldLevel;
+    }
+
+    /**
+     * Gets the new level of the player
+     *
+     * @return The new (current) level of the player
+     */
+    public int getNewLevel() {
+        return newLevel;
+    }
+
+    public HandlerList getHandlers() {
+        return handlers;
+    }
+
+    public static HandlerList getHandlerList() {
+        return handlers;
+    }
+}

paper-api/src/main/java/org/bukkit/event/player/PlayerListener.java

@@ -213,4 +213,18 @@ public class PlayerListener implements Listener {
      * @param event Relevant event details
      */
     public void onPlayerChangedWorld(PlayerChangedWorldEvent event) {}
+
+    /**
+     * Called when a players level changes
+     *
+     * @param event Relevant event details
+     */
+    public void onPlayerLevelChange(PlayerLevelChangeEvent event) {}
+
+    /**
+     * Called when a players experience changes naturally
+     *
+     * @param event Relevant event details
+     */
+    public void onPlayerExpChange(PlayerExpChangeEvent event) {}
 }