From 5e50620d533eb31b4bce1eb5b1c9a2982f1187c6 Mon Sep 17 00:00:00 2001
From: Bill Kuker <bkuker@billkuker.com>
Date: Tue, 23 Nov 2010 15:58:09 +0000
Subject: [PATCH] Weakened references to static listener types for unit pref
 change and fuel change.

---
 .../rocketry/motorsim/RocketScience.java      | 14 +++++++++--
 .../rocketry/motorsim/fuel/FuelResolver.java  | 24 +++++++++++++++----
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/com/billkuker/rocketry/motorsim/RocketScience.java b/src/com/billkuker/rocketry/motorsim/RocketScience.java
index ed89d6b..b92f63c 100644
--- a/src/com/billkuker/rocketry/motorsim/RocketScience.java
+++ b/src/com/billkuker/rocketry/motorsim/RocketScience.java
@@ -6,6 +6,7 @@ import java.lang.reflect.Modifier;
 import java.text.DecimalFormat;
 import java.text.NumberFormat;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Set;
 import java.util.prefs.Preferences;
 
@@ -17,9 +18,12 @@ import javax.measure.unit.SI;
 import javax.measure.unit.Unit;
 import javax.measure.unit.UnitFormat;
 
+import org.apache.log4j.Logger;
 import org.jscience.physics.amount.Amount;
 
 public class RocketScience {
+	private static final Logger log = Logger.getLogger(RocketScience.class);
+	
 	public static Unit<Pressure> PSI = new ProductUnit<Pressure>(NonSI.POUND_FORCE.divide(NonSI.INCH.pow(2)));
 	public static Unit<Impulse> NEWTON_SECOND = new ProductUnit<Impulse>(SI.NEWTON.times(SI.SECOND));
 	public static Unit<Impulse> POUND_SECOND = new ProductUnit<Impulse>(NonSI.POUND_FORCE.times(SI.SECOND));
@@ -83,10 +87,16 @@ public class RocketScience {
 			preference = up;
 			Preferences prefs = Preferences.userNodeForPackage(RocketScience.class);
 			prefs.put("PreferedUnits", up.toString());
-			for ( WeakReference<UnitPreferenceListener> weak : prefListeners ){
+			Iterator<WeakReference<UnitPreferenceListener>> weakIter = prefListeners.iterator();
+			while (weakIter.hasNext()) {
+				WeakReference<UnitPreferenceListener> weak = weakIter.next();
 				UnitPreferenceListener l = weak.get();
-				if ( l != null )
+				if (l != null) {
 					l.preferredUnitsChanged();
+				} else {
+					log.debug("Weak reference to UPE is null");
+					weakIter.remove();
+				}
 			}
 		}
 		
diff --git a/src/com/billkuker/rocketry/motorsim/fuel/FuelResolver.java b/src/com/billkuker/rocketry/motorsim/fuel/FuelResolver.java
index b8ddfe9..ad9f09f 100644
--- a/src/com/billkuker/rocketry/motorsim/fuel/FuelResolver.java
+++ b/src/com/billkuker/rocketry/motorsim/fuel/FuelResolver.java
@@ -4,18 +4,24 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.lang.ref.WeakReference;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;
 
+import org.apache.log4j.Logger;
+
 import com.billkuker.rocketry.motorsim.Fuel;
 import com.billkuker.rocketry.motorsim.io.MotorIO;
 
 public class FuelResolver {
+	private static final Logger log = Logger.getLogger(FuelResolver.class);
+	
 	public static class FuelNotFound extends Exception {
 		private static final long serialVersionUID = 1L;
 	}
@@ -24,7 +30,7 @@ public class FuelResolver {
 		public void fuelsChanged();
 	}
 
-	private static Set<FuelsChangeListener> listeners = new HashSet<FuelResolver.FuelsChangeListener>();
+	private static Set<WeakReference<FuelsChangeListener>> listeners = new HashSet<WeakReference<FuelResolver.FuelsChangeListener>>();
 	private static Map<URI, Fuel> fuels = new HashMap<URI, Fuel>();
 	private static Map<Fuel, URI> uris = new HashMap<Fuel, URI>();
 
@@ -40,7 +46,7 @@ public class FuelResolver {
 	}
 	
 	public static void addFuelsChangeListener(FuelsChangeListener l){
-		listeners.add(l);
+		listeners.add(new WeakReference<FuelResolver.FuelsChangeListener>(l));
 	}
 	
 	public static void removeFuelsChangeListener(FuelsChangeListener l){
@@ -77,7 +83,17 @@ public class FuelResolver {
 	public static void add(Fuel f, URI uri) {
 		fuels.put(uri, f);
 		uris.put(f, uri);
-		for ( FuelsChangeListener l : listeners )
-			l.fuelsChanged();
+		
+		Iterator<WeakReference<FuelsChangeListener>> weakIter = listeners.iterator();
+		while (weakIter.hasNext()) {
+			WeakReference<FuelsChangeListener> weak = weakIter.next();
+			FuelsChangeListener l = weak.get();
+			if (l != null) {
+				l.fuelsChanged();
+			} else {
+				log.debug("Weak reference to FCL is null");
+				weakIter.remove();
+			}
+		}
 	}
 }
-- 
2.30.2