1 files changed, 33 insertions, 0 deletions
diff --git a/docs/teaching/exercises/answers/Answer4c.java b/docs/teaching/exercises/answers/Answer4c.java
new file mode 100644
index 000000000..54107cf8f
--- /dev/null
+++ b/docs/teaching/exercises/answers/Answer4c.java
@@ -0,0 +1,33 @@
+/* *******************************************************************
+ * Copyright (c) 2002 Palo Alto Research Center, Incorporated (PARC).
+ * All rights reserved. 
+ * This program and the accompanying materials are made available 
+ * under the terms of the Common Public License v1.0 
+ * which accompanies this distribution and is available at 
+ * http://www.eclipse.org/legal/cpl-v10.html 
+ *  
+ * Contributors: 
+ *     PARC     initial implementation 
+ * ******************************************************************/
+
+package answers;
+
+import figures.FigureElement;
+import figures.Group;
+import java.awt.Rectangle;
+
+aspect Answer4c {
+    private Rectangle Group.cache = null;
+
+    Rectangle around(Group g):
+            execution(Rectangle Group.getBounds()) && this(g) {
+	if (g.cache == null) {
+	    g.cache = proceed(g);
+	}
+	return g.cache;
+    }
+
+    before(Group g): call(void move(int, int)) && target(g) {
+	g.cache = null;
+    }
+}