3 files changed, 14 insertions, 2 deletions
diff --git a/core/src/main/java/coffee/liz/ecs/DAGWorld.java b/core/src/main/java/coffee/liz/ecs/DAGWorld.java
index f3ad30b..dea83ef 100644
--- a/core/src/main/java/coffee/liz/ecs/DAGWorld.java
+++ b/core/src/main/java/coffee/liz/ecs/DAGWorld.java
@@ -153,4 +153,13 @@ public class DAGWorld<T> implements World<T> {
 
 		return Collections.unmodifiableList(result);
 	}
+
+    @Override
+    public void close() throws Exception {
+        for (final System<T> system : systemExecutionOrder) {
+            system.close();
+        }
+        componentCache.clear();
+        entities.clear();
+    }
 }
diff --git a/core/src/main/java/coffee/liz/ecs/model/System.java b/core/src/main/java/coffee/liz/ecs/model/System.java
index 220b917..cc46f39 100644
--- a/core/src/main/java/coffee/liz/ecs/model/System.java
+++ b/core/src/main/java/coffee/liz/ecs/model/System.java
@@ -9,7 +9,7 @@ import java.util.Collection;
  * @param <T>
  *            is the state of the stuff outside the {@link World}.
  */
-public interface System<T> {
+public interface System<T> extends AutoCloseable {
 	/**
 	 * {@link System} clazzes that must run before this system.
 	 *
@@ -26,4 +26,7 @@ public interface System<T> {
 	 *            Is the timestep.
 	 */
 	void update(final World<T> world, final T state, final Duration dt);
+
+    @Override
+    default void close() {}
 }
diff --git a/core/src/main/java/coffee/liz/ecs/model/World.java b/core/src/main/java/coffee/liz/ecs/model/World.java
index 96c7a74..05363e8 100644
--- a/core/src/main/java/coffee/liz/ecs/model/World.java
+++ b/core/src/main/java/coffee/liz/ecs/model/World.java
@@ -10,7 +10,7 @@ import java.util.Set;
  * @param <T>
  *            is the state of the stuff outside the world.
  */
-public interface World<T> {
+public interface World<T> extends AutoCloseable {
 	/**
 	 * Create unique {@link Entity} in the {@link World}.
 	 *