Use Collections.singleton() where ArrayList has only one element.

This has performance benefits. On my machine it's nearly twice as fast.

src/java/org/jivesoftware/openfire/MulticastRouter.java

@@ -22,6 +22,7 @@ package org.jivesoftware.openfire;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -396,9 +397,7 @@ public class MulticastRouter extends BasicModule implements ServerFeaturesProvid
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add(NAMESPACE);
-        return features.iterator();
+        return Collections.singleton(NAMESPACE).iterator();
     }
 
     @Override

src/java/org/jivesoftware/openfire/commands/AdHocCommandHandler.java

@@ -96,18 +96,14 @@ public class AdHocCommandHandler extends IQHandler
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add(NAMESPACE);
-        return features.iterator();
+        return Collections.singleton(NAMESPACE).iterator();
     }
 
     public Iterator<Element> getIdentities(String name, String node, JID senderJID) {
-        ArrayList<Element> identities = new ArrayList<Element>();
         Element identity = DocumentHelper.createElement("identity");
         identity.addAttribute("category", "automation");
         identity.addAttribute("type", NAMESPACE.equals(node) ? "command-list" : "command-node");
-        identities.add(identity);
-        return identities.iterator();
+        return Collections.singleton(identity).iterator();
     }
 
     public Iterator<String> getFeatures(String name, String node, JID senderJID) {

src/java/org/jivesoftware/openfire/disco/IQDiscoItemsHandler.java

@@ -413,11 +413,7 @@ public class IQDiscoItemsHandler extends IQHandler implements ServerFeaturesProv
     }
 
     public Iterator<String> getFeatures() {
-        List<String> features = new ArrayList<String>();
-        features.add("http://jabber.org/protocol/disco#items");
-        // TODO Comment out this line when publishing of client items is implemented
-        //features.add("http://jabber.org/protocol/disco#publish");
-        return features.iterator();
+        return Collections.singleton(NAMESPACE_DISCO_ITEMS).iterator();
     }
 
     public void joinedCluster() {

src/java/org/jivesoftware/openfire/filetransfer/proxy/FileTransferProxy.java

@@ -24,8 +24,8 @@ import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
-import java.util.List;
 import java.util.Map;
 
 import org.dom4j.DocumentHelper;
@@ -306,30 +306,25 @@ public class FileTransferProxy extends BasicModule
     }
 
     public Iterator<DiscoServerItem> getItems() {
-        List<DiscoServerItem> items = new ArrayList<DiscoServerItem>();
         if(!isEnabled()) {
-            return items.iterator();
+            return Collections.emptyIterator();
         }
 
         final DiscoServerItem item = new DiscoServerItem(new JID(
 			getServiceDomain()), "Socks 5 Bytestreams Proxy", null, null, this,
 			this);
-		items.add(item);
         
-        return items.iterator();
+        return Collections.singleton(item).iterator();
     }
 
     public Iterator<Element> getIdentities(String name, String node, JID senderJID) {
-        List<Element> identities = new ArrayList<Element>();
         // Answer the identity of the proxy
         Element identity = DocumentHelper.createElement("identity");
         identity.addAttribute("category", "proxy");
         identity.addAttribute("name", "SOCKS5 Bytestreams Service");
         identity.addAttribute("type", "bytestreams");
 
-        identities.add(identity);
-
-        return identities.iterator();
+        return Collections.singleton(identity).iterator();
     }
 
     public Iterator<String> getFeatures(String name, String node, JID senderJID) {

src/java/org/jivesoftware/openfire/handler/IQLastActivityHandler.java

@@ -30,7 +30,7 @@ import org.jivesoftware.openfire.user.UserNotFoundException;
 import org.xmpp.packet.IQ;
 import org.xmpp.packet.PacketError;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 
 /**
@@ -116,9 +116,7 @@ public class IQLastActivityHandler extends IQHandler implements ServerFeaturesPr
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add("jabber:iq:last");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:last").iterator();
     }
 
     @Override

src/java/org/jivesoftware/openfire/handler/IQOfflineMessagesHandler.java

@@ -141,22 +141,18 @@ public class IQOfflineMessagesHandler extends IQHandler implements ServerFeature
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add(NAMESPACE);
-        return features.iterator();
+        return Collections.singleton(NAMESPACE).iterator();
     }
 
     public Iterator<Element> getIdentities(String name, String node, JID senderJID) {
-        ArrayList<Element> identities = new ArrayList<Element>();
         Element identity = DocumentHelper.createElement("identity");
         identity.addAttribute("category", "automation");
         identity.addAttribute("type", "message-list");
-        identities.add(identity);
-        return identities.iterator();
+        return Collections.singleton(identity).iterator();
     }
 
     public Iterator<String> getFeatures(String name, String node, JID senderJID) {
-        return Collections.singletonList(NAMESPACE).iterator();
+        return Collections.singleton(NAMESPACE).iterator();
     }
 
     public DataForm getExtendedInfo(String name, String node, JID senderJID) {

src/java/org/jivesoftware/openfire/handler/IQPrivacyHandler.java

@@ -36,7 +36,7 @@ import org.xmpp.packet.IQ;
 import org.xmpp.packet.JID;
 import org.xmpp.packet.PacketError;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -416,9 +416,7 @@ public class IQPrivacyHandler extends IQHandler
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add("jabber:iq:privacy");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:privacy").iterator();
     }
 
     public void userCreated(User user, Map params) {

src/java/org/jivesoftware/openfire/handler/IQPrivateHandler.java

@@ -30,9 +30,8 @@ import org.jivesoftware.openfire.disco.ServerFeaturesProvider;
 import org.xmpp.packet.IQ;
 import org.xmpp.packet.PacketError;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
-import java.util.List;
 
 /**
  * Implements the TYPE_IQ jabber:iq:private protocol. Clients
@@ -117,8 +116,6 @@ public class IQPrivateHandler extends IQHandler implements ServerFeaturesProvide
     }
 
     public Iterator<String> getFeatures() {
-        List<String> features = new ArrayList<String>();
-        features.add("jabber:iq:private");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:private").iterator();
     }
 }

src/java/org/jivesoftware/openfire/handler/IQRegisterHandler.java

@@ -23,7 +23,7 @@ package org.jivesoftware.openfire.handler;
 import gnu.inet.encoding.Stringprep;
 import gnu.inet.encoding.StringprepException;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
@@ -470,8 +470,6 @@ public class IQRegisterHandler extends IQHandler implements ServerFeaturesProvid
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add("jabber:iq:register");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:register").iterator();
     }
 }

src/java/org/jivesoftware/openfire/handler/IQRosterHandler.java

@@ -22,7 +22,7 @@ package org.jivesoftware.openfire.handler;
 
 import gnu.inet.encoding.IDNAException;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Set;
@@ -345,8 +345,6 @@ public class IQRosterHandler extends IQHandler implements ServerFeaturesProvider
 
     @Override
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add("jabber:iq:roster");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:roster").iterator();
     }
 }
\ No newline at end of file

src/java/org/jivesoftware/openfire/handler/IQVersionHandler.java

@@ -30,9 +30,8 @@ import org.jivesoftware.openfire.disco.ServerFeaturesProvider;
 import org.xmpp.packet.IQ;
 import org.xmpp.packet.PacketError;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
-import java.util.List;
 
 /**
  * Implements the TYPE_IQ jabber:iq:version protocol (version info). Allows
@@ -92,8 +91,6 @@ public class IQVersionHandler extends IQHandler implements ServerFeaturesProvide
     }
 
     public Iterator<String> getFeatures() {
-        List<String> features = new ArrayList<String>();
-        features.add("jabber:iq:version");
-        return features.iterator();
+        return Collections.singleton("jabber:iq:version").iterator();
     }
 }
\ No newline at end of file

src/java/org/jivesoftware/openfire/muc/spi/MultiUserChatServiceImpl.java

@@ -976,9 +976,7 @@ public class MultiUserChatServiceImpl implements Component, MultiUserChatService
     }
 
     public void removeUserAllowedToCreate(JID userJID) {
-        List<JID> asList = new ArrayList<JID>();
-        asList.add(userJID);
-    	removeUsersAllowedToCreate(asList);
+    	removeUsersAllowedToCreate(Collections.singleton(userJID));
     }
 
     public void initialize(XMPPServer server) {

src/java/org/jivesoftware/openfire/net/DNSUtil.java

@@ -194,7 +194,7 @@ public class DNSUtil {
             Attribute srvRecords = dnsLookup.get("SRV");
             if (srvRecords == null) {
                 logger.debug("No SRV record found for domain: " + lookup);
-                return new ArrayList<HostAddress>();
+                return Collections.emptyList();
             }
             WeightedHostAddress[] hosts = new WeightedHostAddress[srvRecords.size()];
             for (int i = 0; i < srvRecords.size(); i++) {
@@ -209,7 +209,7 @@ public class DNSUtil {
         catch (NamingException e) {
             logger.error("Can't process DNS lookup!", e);
         }
-        return new ArrayList<HostAddress>();
+        return Collections.emptyList();
     }
 
     /**

src/java/org/jivesoftware/openfire/pep/IQPEPHandler.java

@@ -21,7 +21,7 @@
 package org.jivesoftware.openfire.pep;
 
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.ExecutorService;
@@ -266,12 +266,10 @@ public class IQPEPHandler extends IQHandler implements ServerIdentitiesProvider,
      * the PEP identity to the respective disco#info results.
      */
     public Iterator<Element> getIdentities() {
-        ArrayList<Element> identities = new ArrayList<Element>();
         Element identity = DocumentHelper.createElement("identity");
         identity.addAttribute("category", "pubsub");
         identity.addAttribute("type", "pep");
-        identities.add(identity);
-        return identities.iterator();
+        return Collections.singleton(identity).iterator();
     }
 
     /**

src/java/org/jivesoftware/openfire/vcard/VCardManager.java

@@ -20,7 +20,7 @@
 
 package org.jivesoftware.openfire.vcard;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.StringTokenizer;
@@ -310,9 +310,7 @@ public class VCardManager extends BasicModule implements ServerFeaturesProvider
     }
 
     public Iterator<String> getFeatures() {
-        ArrayList<String> features = new ArrayList<String>();
-        features.add("vcard-temp");
-        return features.iterator();
+        return Collections.singleton("vcard-temp").iterator();
     }
 
     private class EventHandler extends UserEventAdapter {