Memory management optimisation: help garbage collection by avoiding repeated instantiations of immutable arrays (empty arrays of String, Message, Flag, Address)

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

@@ -115,7 +115,7 @@ public class Address
         if (addressList == null
                 && !"".equals(addressList))
         {
-            return new Address[] {};
+            return EMPTY_ADDRESS_ARRAY;
         }
         try
         {
@@ -145,7 +145,7 @@ public class Address
         catch (ParseException pe)
         {
         }
-        return addresses.toArray(new Address[] {});
+        return addresses.toArray(EMPTY_ADDRESS_ARRAY);
     }
 
     @Override

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

@@ -8,6 +8,8 @@ import com.fsck.k9.activity.MessageReference;
 
 public abstract class Message implements Part, Body
 {
+    private static final Flag[] EMPTY_FLAG_ARRAY = new Flag[0];
+
     private MessageReference mReference = null;
 
     public enum RecipientType
@@ -156,7 +158,7 @@ public abstract class Message implements Part, Body
      */
     public Flag[] getFlags()
     {
-        return mFlags.toArray(new Flag[] {});
+        return mFlags.toArray(EMPTY_FLAG_ARRAY);
     }
 
     public void setFlag(Flag flag, boolean set) throws MessagingException

src/com/fsck/k9/mail/internet/MimeHeader.java

@@ -13,6 +13,8 @@ import java.util.*;
 
 public class MimeHeader
 {
+    private static final String[] EMPTY_STRING_ARRAY = new String[0];
+
     /**
      * Application specific header that contains Store specific information about an attachment.
      * In IMAP this contains the IMAP BODYSTRUCTURE part id so that the ImapStore can later
@@ -93,7 +95,7 @@ public class MimeHeader
         {
             return null;
         }
-        return values.toArray(new String[] {});
+        return values.toArray(EMPTY_STRING_ARRAY);
     }
 
     public void removeHeader(String name)

src/com/fsck/k9/mail/store/ImapStore.java

@@ -83,6 +83,10 @@ public class ImapStore extends Store
     private static final String CAPABILITY_COMPRESS_DEFLATE = "COMPRESS=DEFLATE";
     private static final String COMMAND_COMPRESS_DEFLATE = "COMPRESS DEFLATE";
 
+    private static final Message[] EMPTY_MESSAGE_ARRAY = new Message[0];
+
+    private static final String[] EMPTY_STRING_ARRAY = new String[0];
+
     private String mHost;
     private int mPort;
     private String mUsername;
@@ -1091,7 +1095,7 @@ public class ImapStore extends Store
             {
                 throw ioExceptionHandler(mConnection, ioe);
             }
-            return messages.toArray(new Message[] {});
+            return messages.toArray(EMPTY_MESSAGE_ARRAY);
         }
 
 
@@ -1123,7 +1127,7 @@ public class ImapStore extends Store
                             }
                         }
                     }
-                    uids = tempUids.toArray(new String[] {});
+                    uids = tempUids.toArray(EMPTY_STRING_ARRAY);
                 }
                 for (int i = 0, count = uids.length; i < count; i++)
                 {
@@ -1143,7 +1147,7 @@ public class ImapStore extends Store
             {
                 throw ioExceptionHandler(mConnection, ioe);
             }
-            return messages.toArray(new Message[] {});
+            return messages.toArray(EMPTY_MESSAGE_ARRAY);
         }
 
         @Override

src/com/fsck/k9/mail/store/LocalStore.java

@@ -37,6 +37,8 @@ import java.util.regex.Matcher;
 public class LocalStore extends Store implements Serializable
 {
 
+    private static final Message[] EMPTY_MESSAGE_ARRAY = new Message[0];
+
     /**
      * Immutable empty {@link String} array
      */
@@ -805,7 +807,7 @@ public class LocalStore extends Store implements Serializable
             }
         }
 
-        return messages.toArray(new Message[] {});
+        return messages.toArray(EMPTY_MESSAGE_ARRAY);
 
     }
 
@@ -1498,7 +1500,7 @@ public class LocalStore extends Store implements Serializable
 
                 cursor = mDb.rawQuery(
                              "SELECT message_id, name, value FROM headers " + "WHERE message_id in ( " + questions + ") ",
-                             ids.toArray(new String[] {}));
+                             ids.toArray(EMPTY_STRING_ARRAY));
 
 
                 while (cursor.moveToNext())
@@ -1596,7 +1598,7 @@ public class LocalStore extends Store implements Serializable
                     messages.add(message);
                 }
             }
-            return messages.toArray(new Message[] {});
+            return messages.toArray(EMPTY_MESSAGE_ARRAY);
         }
 
         @Override

src/com/fsck/k9/mail/store/WebDavStore.java

@@ -73,6 +73,10 @@ public class WebDavStore extends Store
 
     private static final Flag[] PERMANENT_FLAGS = { Flag.DELETED, Flag.SEEN, Flag.ANSWERED };
 
+    private static final String[] EMPTY_STRING_ARRAY = new String[0];
+
+    private static final Message[] EMPTY_MESSAGE_ARRAY = new Message[0];
+
     private int mConnectionSecurity;
     private String mUsername; /* Stores the username for authentications */
     private String alias;
@@ -1448,7 +1452,7 @@ public class WebDavStore extends Store
                 }
             }
 
-            return messages.toArray(new Message[] {});
+            return messages.toArray(EMPTY_MESSAGE_ARRAY);
         }
 
 
@@ -1467,7 +1471,7 @@ public class WebDavStore extends Store
             if (uids == null ||
                     uids.length == 0)
             {
-                return messageList.toArray(new Message[] {});
+                return messageList.toArray(EMPTY_MESSAGE_ARRAY);
             }
 
             for (int i = 0, count = uids.length; i < count; i++)
@@ -1485,7 +1489,7 @@ public class WebDavStore extends Store
                     listener.messageFinished(message, i, count);
                 }
             }
-            messages = messageList.toArray(new Message[] {});
+            messages = messageList.toArray(EMPTY_MESSAGE_ARRAY);
 
             return messages;
         }
@@ -2298,7 +2302,7 @@ public class WebDavStore extends Store
 
         public String[] getHeaderList()
         {
-            return this.mHeaders.toArray(new String[] {});
+            return this.mHeaders.toArray(EMPTY_STRING_ARRAY);
         }
 
         public void setReadStatus(boolean status)
@@ -2430,7 +2434,7 @@ public class WebDavStore extends Store
                 hrefs.add(href);
             }
 
-            return hrefs.toArray(new String[] {});
+            return hrefs.toArray(EMPTY_STRING_ARRAY);
         }
 
         /**
@@ -2445,7 +2449,7 @@ public class WebDavStore extends Store
                 uids.add(uid);
             }
 
-            return uids.toArray(new String[] {});
+            return uids.toArray(EMPTY_STRING_ARRAY);
         }
 
         /**