start on some javadocs

api/src/main/java/lol/pyr/znpcsplus/api/NpcApiProvider.java

@@ -11,6 +11,11 @@ public class NpcApiProvider {
         throw new UnsupportedOperationException();
     }
 
+    /**
+     * Static method that returns the api instance of the plugin
+     *
+     * @return The instance of the api for the ZNPCsPlus plugin
+     */
     public static NpcApi get() {
         if (api == null) throw new IllegalStateException(
                 "ZNPCsPlus plugin isn't enabled yet!\n" +
@@ -19,11 +24,19 @@ public class NpcApiProvider {
         return api;
     }
 
+    /**
+     * Internal method used to register the main instance of the plugin as the api provider
+     * You probably shouldn't call this method under any circumstances
+     */
     public static void register(Plugin plugin, NpcApi api) {
         NpcApiProvider.api = api;
         Bukkit.getServicesManager().register(NpcApi.class, api, plugin, ServicePriority.Normal);
     }
 
+    /**
+     * Internal method used to unregister the plugin from the provider when the plugin shuts down
+     * You probably shouldn't call this method under any circumstances
+     */
     public static void unregister() {
         Bukkit.getServicesManager().unregister(api);
         NpcApiProvider.api = null;

api/src/main/java/lol/pyr/znpcsplus/api/entity/EntityProperty.java

@@ -1,7 +1,25 @@
 package lol.pyr.znpcsplus.api.entity;
 
+/**
+ * Class that represents a unique property
+ * @param <T> The type of the value of this property
+ */
 public interface EntityProperty<T> {
+    /**
+     * The default value of this property, if this is provided in {@link PropertyHolder#setProperty(EntityProperty, Object)}
+     * as the value the property will be removed from the holder
+     *
+     * @return The default value of this property
+     */
     T getDefaultValue();
+
+    /**
+     * @return The name of this property
+     */
     String getName();
+
+    /**
+     * @return Whether this property can be modified by players using commands
+     */
     boolean isPlayerModifiable();
 }

api/src/main/java/lol/pyr/znpcsplus/api/entity/EntityPropertyRegistry.java

@@ -2,9 +2,40 @@ package lol.pyr.znpcsplus.api.entity;
 
 import java.util.Collection;
 
+/**
+ * Class responsible for providing entity property keys
+ * Some property keys are only registered in certain situations for example different minecraft versions
+ */
 public interface EntityPropertyRegistry {
+    /**
+     * @return All of the possible property keys
+     */
     Collection<EntityProperty<?>> getAll();
+
+    /**
+     * Get a property key by it's name
+     *
+     * @param name The name of a property key
+     * @return The property key corresponding to the name or null if there is none
+     */
     EntityProperty<?> getByName(String name);
+
+    /**
+     * Get a property key by it's name and automatically cast the property to the proper type
+     * If you don't know the type of the property you are requesting use {@link EntityPropertyRegistry#getByName(String)} instead
+     *
+     * @param name The name of a property key
+     * @param type The class of the expected type of the returned property key
+     * @return The property key corresponding to the name
+     * @param <T> The expected type of the returned property key
+     */
     <T> EntityProperty<T> getByName(String name, Class<T> type);
+
+    /**
+     * Register a dummy property that can be used to store unique information per npc
+     *
+     * @param name The name of the new property
+     * @param type The type of the new property
+     */
     void registerDummy(String name, Class<?> type);
 }

api/src/main/java/lol/pyr/znpcsplus/api/entity/PropertyHolder.java

@@ -2,9 +2,40 @@ package lol.pyr.znpcsplus.api.entity;
 
 import java.util.Set;
 
+/**
+ * Represents classes that have property values attatched to them
+ */
 public interface PropertyHolder {
+    /**
+     * Method used to get the value of a property from a property holder
+     *
+     * @param key Unique key representing a property
+     * @return The value associated with the provided property key & this holder
+     * @param <T> The type of the property value
+     */
     <T> T getProperty(EntityProperty<T> key);
+
+    /**
+     * Method used to check if a property holder has a value set for a specific property key
+     *
+     * @param key Unique key representing a property
+     * @return Whether this holder has a value set for the provided key
+     */
     boolean hasProperty(EntityProperty<?> key);
+
+    /**
+     * Method used to set a value for the provided key on this property holder
+     *
+     * @param key Unique key representing a property
+     * @param value The value to assign to the property key on this holder
+     * @param <T> The type of the property value
+     */
     <T> void setProperty(EntityProperty<T> key, T value);
+
+    /**
+     * Method used to get a set of all of the property keys that this holder has a value for
+     *
+     * @return List of property keys
+     */
     Set<EntityProperty<?>> getAppliedProperties();
 }

api/src/main/java/lol/pyr/znpcsplus/api/npc/Npc.java

@@ -25,4 +25,7 @@ public interface Npc extends PropertyHolder {
     void hide(Player player);
     void show(Player player);
     void respawn(Player player);
+
+    void setHeadRotation(Player player, float yaw, float pitch);
+    void setHeadRotation(float yaw, float pitch);
 }