use isEmpty instead of size() == 0 for clarify

src/com/fsck/k9/Preferences.java

@@ -39,7 +39,7 @@ public class Preferences {
     private Preferences(Context context) {
         mStorage = Storage.getStorage(context);
         mContext = context;
-        if (mStorage.size() == 0) {
+        if (mStorage.isEmpty()) {
             Log.i(K9.LOG_TAG, "Preferences storage is zero-size, importing from Android-style preferences");
             Editor editor = mStorage.edit();
             editor.copy(context.getSharedPreferences("AndroidMail.Main", Context.MODE_PRIVATE));

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

@@ -1056,7 +1056,7 @@ public class MessageCompose extends K9Activity implements OnClickListener,
     }
 
     private boolean addRecipients(TextView view, List<String> recipients) {
-        if (recipients == null || recipients.size() == 0) {
+        if (recipients == null || recipients.isEmpty()) {
             return false;
         }
 

src/com/fsck/k9/cache/EmailProviderCache.java

@@ -101,7 +101,7 @@ public class EmailProviderCache {
                 Map<String, String> map = mMessageCache.get(messageId);
                 if (map != null) {
                     map.remove(columnName);
-                    if (map.size() == 0) {
+                    if (map.isEmpty()) {
                         mMessageCache.remove(messageId);
                     }
                 }
@@ -115,7 +115,7 @@ public class EmailProviderCache {
                 Map<String, String> map = mThreadCache.get(threadRootId);
                 if (map != null) {
                     map.remove(columnName);
-                    if (map.size() == 0) {
+                    if (map.isEmpty()) {
                         mThreadCache.remove(threadRootId);
                     }
                 }

src/com/fsck/k9/cache/EmailProviderCacheCursor.java

@@ -108,7 +108,7 @@ public class EmailProviderCacheCursor extends CursorWrapper {
 
     @Override
     public boolean moveToPosition(int position) {
-        if (mHiddenRows.size() == 0) {
+        if (mHiddenRows.isEmpty()) {
             return super.moveToPosition(position);
         }
 
@@ -126,7 +126,7 @@ public class EmailProviderCacheCursor extends CursorWrapper {
 
     @Override
     public int getPosition() {
-        if (mHiddenRows.size() == 0) {
+        if (mHiddenRows.isEmpty()) {
             return super.getPosition();
         }
 

src/com/fsck/k9/fragment/MessageListFragment.java

@@ -1814,7 +1814,7 @@ public class MessageListFragment extends Fragment implements OnItemClickListener
             }
 
             List<String> folderNames = mSearch.getFolderNames();
-            return (folderNames.size() == 0 || folderNames.contains(folder));
+            return (folderNames.isEmpty() || folderNames.contains(folder));
         }
     }
 
@@ -2362,7 +2362,7 @@ public class MessageListFragment extends Fragment implements OnItemClickListener
     }
 
     private void setFlagForSelected(final Flag flag, final boolean newState) {
-        if (mSelected.size() == 0) {
+        if (mSelected.isEmpty()) {
             return;
         }
 
@@ -2586,7 +2586,7 @@ public class MessageListFragment extends Fragment implements OnItemClickListener
     private boolean checkCopyOrMovePossible(final List<Message> messages,
             final FolderOperation operation) {
 
-        if (messages.size() == 0) {
+        if (messages.isEmpty()) {
             return false;
         }
 
@@ -3515,7 +3515,7 @@ public class MessageListFragment extends Fragment implements OnItemClickListener
     }
 
     private void cleanupSelected(Cursor cursor) {
-        if (mSelected.size() == 0) {
+        if (mSelected.isEmpty()) {
             return;
         }
 
@@ -3534,7 +3534,7 @@ public class MessageListFragment extends Fragment implements OnItemClickListener
      * Starts or finishes the action mode when necessary.
      */
     private void resetActionMode() {
-        if (mSelected.size() == 0) {
+        if (mSelected.isEmpty()) {
             if (mActionMode != null) {
                 mActionMode.finish();
             }

src/com/fsck/k9/helper/Contacts.java

@@ -302,7 +302,7 @@ public class Contacts {
                 }
 
                 // Return 'null' if no email addresses have been found
-                if (email.size() == 0) {
+                if (email.isEmpty()) {
                     return null;
                 }
 

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

@@ -1097,7 +1097,7 @@ public class ImapStore extends Store {
                 throw new MessagingException("ImapFolder.copyMessages passed non-ImapFolder");
             }
 
-            if (messages.size() == 0) {
+            if (messages.isEmpty()) {
                 return null;
             }
 
@@ -1193,7 +1193,7 @@ public class ImapStore extends Store {
 
         @Override
         public Map<String, String> moveMessages(List<? extends Message> messages, Folder folder) throws MessagingException {
-            if (messages.size() == 0)
+            if (messages.isEmpty())
                 return null;
             Map<String, String> uidMap = copyMessages(messages, folder);
             setFlags(messages, Collections.singleton(Flag.DELETED), true);
@@ -1202,7 +1202,7 @@ public class ImapStore extends Store {
 
         @Override
         public void delete(List<? extends Message> messages, String trashFolderName) throws MessagingException {
-            if (messages.size() == 0)
+            if (messages.isEmpty())
                 return;
 
             if (trashFolderName == null || getName().equalsIgnoreCase(trashFolderName)) {
@@ -1435,7 +1435,7 @@ public class ImapStore extends Store {
         @Override
         public void fetch(List<? extends Message> messages, FetchProfile fp, MessageRetrievalListener listener)
         throws MessagingException {
-            if (messages == null || messages.size() == 0) {
+            if (messages == null || messages.isEmpty()) {
                 return;
             }
             checkOpen(); //only need READ access
@@ -2036,7 +2036,7 @@ public class ImapStore extends Store {
                  * with the behavior of other similar methods (copyMessages, moveMessages) which
                  * return null.
                  */
-                return (uidMap.size() == 0) ? null : uidMap;
+                return (uidMap.isEmpty()) ? null : uidMap;
             } catch (IOException ioe) {
                 throw ioExceptionHandler(mConnection, ioe);
             }

src/com/fsck/k9/mail/store/Pop3Store.java

@@ -763,7 +763,7 @@ public class Pop3Store extends Store {
         @Override
         public void fetch(List<? extends Message> messages, FetchProfile fp, MessageRetrievalListener listener)
         throws MessagingException {
-            if (messages == null || messages.size() == 0) {
+            if (messages == null || messages.isEmpty()) {
                 return;
             }
             List<String> uids = new ArrayList<String>();

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

@@ -1501,7 +1501,7 @@ public class WebDavStore extends Store {
         public void fetch(List<? extends Message> messages, FetchProfile fp, MessageRetrievalListener listener)
         throws MessagingException {
             if (messages == null ||
-                    messages.size() == 0) {
+                    messages.isEmpty()) {
                 return;
             }
 
@@ -1654,7 +1654,7 @@ public class WebDavStore extends Store {
             String[] uids;
 
             if (startMessages == null ||
-                    startMessages.size() == 0) {
+                    startMessages.isEmpty()) {
                 return;
             }
 
@@ -1724,7 +1724,7 @@ public class WebDavStore extends Store {
             List<Message> messages = new ArrayList<Message>(10);
 
             if (startMessages == null ||
-                    startMessages.size() == 0) {
+                    startMessages.isEmpty()) {
                 return;
             }
 

src/com/fsck/k9/preferences/Settings.java

@@ -51,7 +51,7 @@ public class Settings {
             SortedMap<Integer, SettingsDescription> headMap = versions.headMap(version + 1);
 
             // Skip this setting if it was introduced after 'version'
-            if (headMap.size() == 0) {
+            if (headMap.isEmpty()) {
                 continue;
             }
 

src/com/fsck/k9/preferences/Storage.java

@@ -290,8 +290,8 @@ public class Storage implements SharedPreferences {
         }
     }
 
-    public long size() {
+    public boolean isEmpty() {
-        return storage.size();
+        return storage.isEmpty();
     }
 
     //@Override

src/com/fsck/k9/search/LocalSearch.java

@@ -328,7 +328,7 @@ public class LocalSearch implements SearchSpecification {
      */
     @Override
     public String[] getAccountUuids() {
-        if (mAccountUuids.size() == 0) {
+        if (mAccountUuids.isEmpty()) {
             return new String[] { SearchSpecification.ALL_ACCOUNTS };
         }
 
@@ -343,7 +343,7 @@ public class LocalSearch implements SearchSpecification {
      * @return {@code true} if all accounts should be searched.
      */
     public boolean searchAllAccounts() {
-        return (mAccountUuids.size() == 0);
+        return (mAccountUuids.isEmpty());
     }
 
     /**