From 6ede239232cade1dbd454d58f4e853366e422099 Mon Sep 17 00:00:00 2001
From: acolyer <acolyer>
Date: Fri, 17 Dec 2004 13:25:52 +0000
Subject: [PATCH] incorporate tim peierls suggestion from mailing list

---
 docs/adk15ProgGuideDB/pertypewithin.xml | 31 +++++++++----------------
 1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/docs/adk15ProgGuideDB/pertypewithin.xml b/docs/adk15ProgGuideDB/pertypewithin.xml
index e3f5ec0ae..ec099c1fd 100644
--- a/docs/adk15ProgGuideDB/pertypewithin.xml
+++ b/docs/adk15ProgGuideDB/pertypewithin.xml
@@ -54,21 +54,16 @@
 
   	<programlisting><![CDATA[
   	 public aspect InstanceTracking pertypewithin(org.xyz..*) {
-  	 
-  	   private Set<WeakReference<Object>> instances = new HashSet<WeakReference<Object>>();
+
+	   // use WeakHashMap for auto-garbage collection of keys  	 
+  	   private Map<?,Boolean> instances = new WeakHashMap<?,Boolean>();
   	   
   	   after(Object o) returning : execution(new(..)) {
-  	     instances.add(new WeakReference<Object>(o);
+  	     instances.put(o,true);
   	   }
   	 
-  	   public Set<Object> getInstances() {
-  	      Set<Object> result = new HashSet<Object>();
-  	      for(WeakReference<Object> ref : instances) {
-  	          if (ref.get() != null) {
-  	           result.add(ref.get());
-  	          }
-  	      }
-  	      return result;
+  	   public Set<?> getInstances() {
+  	      return instances.keySet();
   	   }
   	 }
 	]]></programlisting>
@@ -95,21 +90,17 @@
   	<programlisting><![CDATA[
   	 public aspect InstanceTracking<T> pertypewithin(org.xyz..*) {
   	 
-  	   private Set<WeakReference<T>> instances = new HashSet<WeakReference<T>>();
+	   // use WeakHashMap for auto-garbage collection of keys  	 
+  	   private Map<T, Boolean> instances = new WeakHashMap<T, Boolean>();
   	   
   	   after(T t) returning : execution(new(..)) {
-  	     instances.add(new WeakReference<T>(t);
+  	     instances.put(t, true);
   	   }
   	 
   	   public Set<T> getInstances() {
-  	      Set<T> result = new HashSet<T>();
-  	      for(WeakReference<T> ref : instances) {
-  	          if (ref.get() != null) {
-  	           result.add(ref.get());
-  	          }
-  	      }
-  	      return result;
+  	   	  return instances.keySet();
   	   }
+  	   
   	 }
 	]]></programlisting>
   
-- 
2.39.5