Code cleanup: Fixed some warnings

src/com/fsck/k9/MessagingControllerPushReceiver.java

@@ -83,12 +83,14 @@ public class MessagingControllerPushReceiver implements PushReceiver
         final CountDownLatch latch = new CountDownLatch(1);
         controller.synchronizeMailbox(account, folder.getName(), new MessagingListener()
         {
+            @Override
             public void synchronizeMailboxFinished(Account account, String folder,
                                                    int totalMessagesInMailbox, int numNewMessages)
             {
                 latch.countDown();
             }
 
+            @Override
             public void synchronizeMailboxFailed(Account account, String folder,
                                                  String message)
             {

src/com/fsck/k9/activity/MessageList.java

@@ -36,8 +36,6 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 

src/com/fsck/k9/activity/MessageReference.java

@@ -8,6 +8,7 @@ public class MessageReference implements Serializable
     public String folderName;
     public String uid;
 
+    @Override
     public boolean equals(Object o)
     {
         if (o instanceof MessageReference == false)
@@ -23,6 +24,20 @@ public class MessageReference implements Serializable
         }
         return false;
     }
+
+    @Override
+    public int hashCode()
+    {
+        final int MULTIPLIER = 31;
+
+        int result = 1;
+        result = MULTIPLIER * result + ((accountUuid == null) ? 0 : accountUuid.hashCode());
+        result = MULTIPLIER * result + ((folderName == null) ? 0 : folderName.hashCode());
+        result = MULTIPLIER * result + ((uid == null) ? 0 : uid.hashCode());
+        return result;
+    }
+
+    @Override
     public String toString()
     {
         return "MessageReference{accountUuid = '" +

src/com/fsck/k9/mail/Message.java

@@ -23,6 +23,7 @@ public abstract class Message implements Part, Body
 
     protected Folder mFolder;
 
+    @Override
     public boolean equals(Object o)
     {
         if (o == null || o instanceof Message == false)
@@ -35,6 +36,17 @@ public abstract class Message implements Part, Body
                 && mUid.equals(other.getUid()));        
     }
     
+    @Override
+    public int hashCode()
+    {
+        final int MULTIPLIER = 31;
+
+        int result = 1;
+        result = MULTIPLIER * result + mFolder.getName().hashCode();
+        result = MULTIPLIER * result + mFolder.getAccount().getUuid().hashCode();
+        result = MULTIPLIER * result + mUid.hashCode();
+        return result;
+    }
     
     public String getUid()
     {