Changed component data handling

Adding empty (null) component data defaults to false
Also added getNumEntities() function
Added a test for getRegistrationsOutOfRange

javaecs/src/main/java/nz/ac/massey/javaecs/ComponentManager.java

@@ -17,14 +17,22 @@ class ComponentManager{
     private Map<Type, ComponentArray> componentArrays = new HashMap<>();
     private Map<Type, Integer> componentPosIndex = new HashMap<>();
     private Map<Integer, Type> indexComponentType = new HashMap<>();
+    private BitSet ignoreEmpty = new BitSet(); // Ignore empty values when deleting data of the index type.
 
     /**
-     * Adds the specified component to the provided entity
+     * Adds the specified component to the provided entity.
+     * <p>
+     * Providing a null Object defaults the value to boolean false
      * @param componentType the class type of the component to add
      * @param componentData the component data to associate
      * @param entity the entity to associate data to
      */
     protected boolean addComponentToEntity(Type componentType, Object componentData, Entity entity){
+        if (componentData == null){
+            // In the case of null component data, insert the boolean false 
+            // (preserves structure by associating data with a null component)
+            return componentArrays.get(componentType).insertData(entity, false);
+        }
         return componentArrays.get(componentType).insertData(entity, componentData);
     }
 

javaecs/src/main/java/nz/ac/massey/javaecs/Engine.java

@@ -208,4 +208,8 @@ public class Engine {
     public SystemManager getSystemManager() {
         return systemManager;
     }
+
+    public int getNumEntities(){
+        return entityManager.getNumEntities();
+    }
 }

javaecs/src/main/java/nz/ac/massey/javaecs/EntityManager.java

@@ -210,4 +210,8 @@ class EntityManager{
             return true;
         }
     }
+
+    protected int getNumEntities(){
+        return maxSize - unusedEntities.size();
+    }
 }

javaecs/src/test/java/nz/ac/massey/javaecs/AppTest.java

@@ -229,6 +229,12 @@ class AppTest {
         assertFalse(gameEngine.registerSystem(TestSystem.class, new TestSystem()));
     }
 
+    @Test
+    void testGetRegistrationsOutOfRange(){
+        Entity entity = Entity.asEntity(25);
+        assertEquals(new BitSet(), gameEngine.entityManager.getRegistrations(entity));
+    }
+
     /**
      * Establish a simple ECS, with a single system and component
      */