Add has() method to ComponentMapper

Some other minor changes:
* Made ComponentType final + package-private
* Made Entity and ComponentType id protected to allow direct access from
  Engine
* Made ComponentType bits protected to allow direct access from Entity
* Made Entity componentBIts protected to allow direct access from
  ComponentMapper and EntitySystem

core/src/com/me/common/ecs/ComponentBag.java

@@ -17,6 +17,10 @@ public class ComponentBag {
         return items[index];
     }
 
+    public boolean contains(int index) {
+        return index < size && items[index] != null;
+    }
+
     public void insert(int index, Component item) {
         if (index >= size) {
             grow((int) (index * 1.5f));

core/src/com/me/common/ecs/ComponentMapper.java

@@ -16,4 +16,8 @@ public class ComponentMapper<T extends Component> {
         return typeClass.cast(engine.getEntityComponent(entity, type));
     }
 
+    public boolean has(Entity entity) {
+        return type.isTypeInMask(entity.componentBits);
+    }
+
 }

core/src/com/me/common/ecs/ComponentType.java

@@ -3,7 +3,7 @@ package com.me.common.ecs;
 import java.util.HashMap;
 import java.util.Map;
 
-public class ComponentType {
+final class ComponentType {
 
     private static final Map<Class<? extends Component>, ComponentType> types = new HashMap<>();
     private static final ComponentType[] typeById = new ComponentType[Long.SIZE];
@@ -11,8 +11,8 @@ public class ComponentType {
     private static long nextBit = 1l;
     private static int nextId = 0;
 
-    private long bits;
-    private int id;
+    protected long bits;
+    protected int id;
 
     private ComponentType() {
         this.bits = nextBit;
@@ -26,7 +26,7 @@ public class ComponentType {
     }
 
     protected int getId() {
-        return this.id;
+        return id;
     }
 
     protected static long getMaskBits(Class<? extends Component>... components) {
@@ -38,11 +38,11 @@ public class ComponentType {
     }
 
     protected static long getTypeBits(Class<? extends Component> component) {
-        return getComponentType(component).getBits();
+        return getComponentType(component).bits;
     }
 
     protected static int getTypeId(Class<? extends Component> component) {
-        return getComponentType(component).getId();
+        return getComponentType(component).id;
     }
 
     protected static ComponentType getById(int id) {
@@ -60,7 +60,7 @@ public class ComponentType {
         }
         type = new ComponentType();
         types.put(component, type);
-        typeById[type.getId()] = type;
+        typeById[type.id] = type;
     }
 
     protected static ComponentType getComponentType(Class<? extends Component> component) {

core/src/com/me/common/ecs/Engine.java

@@ -122,7 +122,7 @@ public class Engine {
         }
 
         for (Entity entity : toRemove) {
-            removeAllEntityComponents(entity.getId());
+            removeAllEntityComponents(entity.id);
             entities.removeValue(entity, true);
             removeEntityFromSystems(entity);
             removedEntities.add(entity);
@@ -173,24 +173,27 @@ public class Engine {
 
     protected void addEntityComponent(Entity entity, Component component) {
         ComponentType type = ComponentType.getComponentType(component.getClass());
-        components[type.getId()].insert(entity.getId(), component);
+        components[type.id].insert(entity.id, component);
         entity.addComponentType(type);
     }
 
 
     protected void removeEntityComponent(Entity entity, Component component) {
         ComponentType type = ComponentType.getComponentType(component.getClass());
-        components[type.getId()].remove(entity.getId());
+        components[type.id].remove(entity.id);
         entity.removeComponentType(type);
     }
 
     protected <T extends Component> T getEntityComponent(Entity entity, Class<T> clazz) {
-        ComponentType type = ComponentType.getComponentType(clazz);
-        return clazz.cast(components[type.getId()].get(entity.getId()));
+        return clazz.cast(components[ComponentType.getTypeId(clazz)].get(entity.id));
     }
 
     protected Component getEntityComponent(Entity entity, ComponentType type) {
-        return components[type.getId()].get(entity.getId());
+        return components[type.id].get(entity.id);
+    }
+
+    protected boolean entityHasComponent(Entity entity, ComponentType type) {
+        return components[type.id].contains(entity.id);
     }
 
     @SuppressWarnings("unchecked")

core/src/com/me/common/ecs/Entity.java

@@ -7,12 +7,12 @@ public final class Entity {
 
     private Engine engine;
 
-    private int id;
+    protected int id;
+    protected long componentBits;
+
     private long uniqueId;
     private boolean active;
 
-    private long componentBits;
-
     protected Entity(Engine engine) {
         this.engine = engine;
         this.active = false;
@@ -66,15 +66,11 @@ public final class Entity {
     }
 
     protected void addComponentType(ComponentType type) {
-        componentBits |= type.getBits();
+        componentBits |= type.bits;
     }
 
     protected void removeComponentType(ComponentType type) {
-        componentBits &= ~type.getBits();
-    }
-
-    protected long getComponentBits() {
-        return componentBits;
+        componentBits &= ~type.bits;
     }
 
     protected void reset() {

core/src/com/me/common/ecs/EntitySystem.java

@@ -27,7 +27,7 @@ public abstract class EntitySystem extends BaseSystem {
     public abstract void processEntity(Entity entity, float dt);
 
     public boolean interestedIn(Entity entity) {
-        return (entity.getComponentBits() & typeBits) == typeBits;
+        return (entity.componentBits & typeBits) == typeBits;
     }
 
     protected void addEntity(Entity entity) {