diff --git a/src/com/fsck/k9/Account.java b/src/com/fsck/k9/Account.java
index 2693b011a..9f8ee925f 100644
--- a/src/com/fsck/k9/Account.java
+++ b/src/com/fsck/k9/Account.java
@@ -1135,7 +1135,7 @@ public class Account implements BaseAccount {
             ident++;
         } while (gotOne);
 
-        if (newIdentities.size() == 0) {
+        if (newIdentities.isEmpty()) {
             String name = prefs.getString(mUuid + ".name", null);
             String email = prefs.getString(mUuid + ".email", null);
             boolean signatureUse = prefs.getBoolean(mUuid  + ".signatureUse", true);
diff --git a/src/com/fsck/k9/Preferences.java b/src/com/fsck/k9/Preferences.java
index f0d0beea8..f30c7e578 100644
--- a/src/com/fsck/k9/Preferences.java
+++ b/src/com/fsck/k9/Preferences.java
@@ -154,7 +154,7 @@ public class Preferences {
 
         if (defaultAccount == null) {
             Collection<Account> accounts = getAvailableAccounts();
-            if (accounts.size() > 0) {
+            if (!accounts.isEmpty()) {
                 defaultAccount = accounts.iterator().next();
                 setDefaultAccount(defaultAccount);
             }
diff --git a/src/com/fsck/k9/activity/Accounts.java b/src/com/fsck/k9/activity/Accounts.java
index 0f76e2416..4bc0d3291 100644
--- a/src/com/fsck/k9/activity/Accounts.java
+++ b/src/com/fsck/k9/activity/Accounts.java
@@ -388,7 +388,7 @@ public class Accounts extends K9ListActivity implements OnItemClickListener, OnC
 
         mAdapter = new AccountsAdapter(newAccounts.toArray(EMPTY_BASE_ACCOUNT_ARRAY));
         getListView().setAdapter(mAdapter);
-        if (newAccounts.size() > 0) {
+        if (!newAccounts.isEmpty()) {
             mHandler.progress(Window.PROGRESS_START);
         }
         pendingWork.clear();
diff --git a/src/com/fsck/k9/activity/MessageCompose.java b/src/com/fsck/k9/activity/MessageCompose.java
index 9ccd357c9..add921109 100644
--- a/src/com/fsck/k9/activity/MessageCompose.java
+++ b/src/com/fsck/k9/activity/MessageCompose.java
@@ -2567,13 +2567,13 @@ public class MessageCompose extends K9Activity implements OnClickListener, OnFoc
 
         // Read subject from the "subject" parameter.
         List<String> subject = uri.getQueryParameters("subject");
-        if (subject.size() > 0) {
+        if (!subject.isEmpty()) {
             mSubjectView.setText(subject.get(0));
         }
 
         // Read message body from the "body" parameter.
         List<String> body = uri.getQueryParameters("body");
-        if (body.size() > 0) {
+        if (!body.isEmpty()) {
             mMessageContentView.setText(body.get(0));
         }
     }
diff --git a/src/com/fsck/k9/activity/MessageList.java b/src/com/fsck/k9/activity/MessageList.java
index 50e911a87..626f522fb 100644
--- a/src/com/fsck/k9/activity/MessageList.java
+++ b/src/com/fsck/k9/activity/MessageList.java
@@ -1977,7 +1977,7 @@ public class MessageList
                 }
             }
 
-            if (messagesToSearch.size() > 0) {
+            if (!messagesToSearch.isEmpty()) {
                 mController.searchLocalMessages(mAccountUuids, mFolderNames, messagesToSearch.toArray(EMPTY_MESSAGE_ARRAY), mQueryString, mIntegrate, mQueryFlags, mForbiddenFlags,
                 new MessagingListener() {
                     @Override
@@ -1987,11 +1987,11 @@ public class MessageList
                 });
             }
 
-            if (messagesToRemove.size() > 0) {
+            if (!messagesToRemove.isEmpty()) {
                 removeMessages(messagesToRemove);
             }
 
-            if (messagesToAdd.size() > 0) {
+            if (!messagesToAdd.isEmpty()) {
                 mHandler.addMessages(messagesToAdd);
             }
 
diff --git a/src/com/fsck/k9/controller/MessagingController.java b/src/com/fsck/k9/controller/MessagingController.java
index 6cd048556..49662d576 100644
--- a/src/com/fsck/k9/controller/MessagingController.java
+++ b/src/com/fsck/k9/controller/MessagingController.java
@@ -296,7 +296,7 @@ public class MessagingController implements Runnable {
                               " Command '" + command.description + "' completed");
 
                     for (MessagingListener l : getListeners(command.listener)) {
-                        l.controllerCommandCompleted(mCommands.size() > 0);
+                        l.controllerCommandCompleted(!mCommands.isEmpty());
                     }
                 }
             } catch (Exception e) {
@@ -417,7 +417,7 @@ public class MessagingController implements Runnable {
 
                 Folder[] folderArray = localFolders.toArray(EMPTY_FOLDER_ARRAY);
 
-                if (refreshRemote || localFolders.size() == 0) {
+                if (refreshRemote || localFolders.isEmpty()) {
                     doRefreshRemote(account, listener);
                     return;
                 }
@@ -1225,7 +1225,7 @@ public class MessagingController implements Runnable {
         messages.clear();
         final ArrayList<Message> largeMessages = new ArrayList<Message>();
         final ArrayList<Message> smallMessages = new ArrayList<Message>();
-        if (unsyncedMessages.size() > 0) {
+        if (!unsyncedMessages.isEmpty()) {
 
             /*
              * Reverse the order of the messages. Depending on the server this may get us
@@ -1481,7 +1481,7 @@ public class MessagingController implements Runnable {
             }
 
         });
-        if (chunk.size() > 0) {
+        if (!chunk.isEmpty()) {
             writeUnsyncedMessages(chunk, localFolder, account, folder);
             chunk.clear();
         }
@@ -2227,7 +2227,7 @@ public class MessagingController implements Runnable {
                 }
             }
 
-            if (messages.size() == 0) {
+            if (messages.isEmpty()) {
                 return;
             }
             remoteFolder.setFlags(messages.toArray(EMPTY_MESSAGE_ARRAY), new Flag[] { flag }, newState);
@@ -4230,7 +4230,7 @@ public class MessagingController implements Runnable {
                 names.add(folder.getName());
             }
 
-            if (names.size() > 0) {
+            if (!names.isEmpty()) {
                 PushReceiver receiver = new MessagingControllerPushReceiver(mApplication, account, this);
                 int maxPushFolders = account.getMaxPushFolders();
 
diff --git a/src/com/fsck/k9/crypto/Apg.java b/src/com/fsck/k9/crypto/Apg.java
index c7417878d..de1a2b77e 100644
--- a/src/com/fsck/k9/crypto/Apg.java
+++ b/src/com/fsck/k9/crypto/Apg.java
@@ -176,7 +176,7 @@ public class Apg extends CryptoProvider {
                                activity.getResources().getString(R.string.insufficient_apg_permissions),
                                Toast.LENGTH_LONG).show();
             }
-            if (keyIds.size() > 0) {
+            if (!keyIds.isEmpty()) {
                 initialKeyIds = new long[keyIds.size()];
                 for (int i = 0, size = keyIds.size(); i < size; ++i) {
                     initialKeyIds[i] = keyIds.get(i);
diff --git a/src/com/fsck/k9/helper/Contacts.java b/src/com/fsck/k9/helper/Contacts.java
index acf97d174..a79f0600a 100644
--- a/src/com/fsck/k9/helper/Contacts.java
+++ b/src/com/fsck/k9/helper/Contacts.java
@@ -187,8 +187,8 @@ public abstract class Contacts {
      */
     public boolean hasContactPicker() {
         if (mHasContactPicker == null) {
-            mHasContactPicker = (mContext.getPackageManager().
-                                 queryIntentActivities(contactPickerIntent(), 0).size() > 0);
+            mHasContactPicker = !(mContext.getPackageManager().
+                                  queryIntentActivities(contactPickerIntent(), 0).isEmpty());
         }
         return mHasContactPicker;
     }
diff --git a/src/com/fsck/k9/mail/internet/MimeHeader.java b/src/com/fsck/k9/mail/internet/MimeHeader.java
index c6b8510c8..f79edd7dc 100644
--- a/src/com/fsck/k9/mail/internet/MimeHeader.java
+++ b/src/com/fsck/k9/mail/internet/MimeHeader.java
@@ -78,7 +78,7 @@ public class MimeHeader {
                 values.add(field.value);
             }
         }
-        if (values.size() == 0) {
+        if (values.isEmpty()) {
             return null;
         }
         return values.toArray(EMPTY_STRING_ARRAY);
diff --git a/src/com/fsck/k9/mail/internet/MimeMultipart.java b/src/com/fsck/k9/mail/internet/MimeMultipart.java
index 4ee381af4..abcd6b510 100644
--- a/src/com/fsck/k9/mail/internet/MimeMultipart.java
+++ b/src/com/fsck/k9/mail/internet/MimeMultipart.java
@@ -73,7 +73,7 @@ public class MimeMultipart extends Multipart {
             writer.write(mPreamble + "\r\n");
         }
 
-        if (mParts.size() == 0) {
+        if (mParts.isEmpty()) {
             writer.write("--" + mBoundary + "\r\n");
         }
 
diff --git a/src/com/fsck/k9/mail/store/ImapStore.java b/src/com/fsck/k9/mail/store/ImapStore.java
index 4c22e812b..eb015c63c 100644
--- a/src/com/fsck/k9/mail/store/ImapStore.java
+++ b/src/com/fsck/k9/mail/store/ImapStore.java
@@ -655,7 +655,7 @@ public class ImapStore extends Store {
                         if (bracketedObj instanceof ImapList) {
                             ImapList bracketed = (ImapList)bracketedObj;
 
-                            if (bracketed.size() > 0) {
+                            if (!bracketed.isEmpty()) {
                                 Object keyObj = bracketed.get(0);
                                 if (keyObj instanceof String) {
                                     String key = (String)keyObj;
@@ -1409,7 +1409,7 @@ public class ImapStore extends Store {
 //                {
 //                    ImapList bracketed = (ImapList)bracketedObj;
 //
-//                    if (bracketed.size() > 0)
+//                    if (!bracketed.isEmpty())
 //                    {
 //                        Object keyObj = bracketed.get(0);
 //                        if (keyObj instanceof String)
@@ -1544,7 +1544,7 @@ public class ImapStore extends Store {
 
                 String contentDisposition = "";
 
-                if (bodyDisposition != null && bodyDisposition.size() > 0) {
+                if (bodyDisposition != null && !bodyDisposition.isEmpty()) {
                     if (!"NIL".equalsIgnoreCase(bodyDisposition.getString(0))) {
                         contentDisposition = bodyDisposition.getString(0).toLowerCase(Locale.US);
                     }
@@ -1816,7 +1816,7 @@ public class ImapStore extends Store {
         private List<ImapResponse> receiveCapabilities(List<ImapResponse> responses) {
             for (ImapResponse response : responses) {
                 ImapList capabilityList = null;
-                if (response.size() > 0 && ImapResponseParser.equalsIgnoreCase(response.get(0), "OK")) {
+                if (!response.isEmpty() && ImapResponseParser.equalsIgnoreCase(response.get(0), "OK")) {
                     for (Object thisPart : response) {
                         if (thisPart instanceof ImapList) {
                             ImapList thisList = (ImapList)thisPart;
@@ -1831,7 +1831,7 @@ public class ImapStore extends Store {
                 }
 
                 if (capabilityList != null) {
-                    if (capabilityList.size() > 0 && ImapResponseParser.equalsIgnoreCase(capabilityList.get(0), CAPABILITY_CAPABILITY)) {
+                    if (!capabilityList.isEmpty() && ImapResponseParser.equalsIgnoreCase(capabilityList.get(0), CAPABILITY_CAPABILITY)) {
                         if (K9.DEBUG) {
                             Log.d(K9.LOG_TAG, "Saving " + capabilityList.size() + " capabilities for " + getLogId());
                         }
@@ -2494,13 +2494,13 @@ public class ImapStore extends Store {
                                     ImapMessage message = new ImapMessage("" + uid, ImapFolderPusher.this);
                                     messages.add(message);
                                 }
-                                if (messages.size() > 0) {
+                                if (!messages.isEmpty()) {
                                     pushMessages(messages, true);
                                 }
 
                             } else {
                                 List<ImapResponse> untaggedResponses = null;
-                                while (storedUntaggedResponses.size() > 0) {
+                                while (!storedUntaggedResponses.isEmpty()) {
                                     if (K9.DEBUG)
                                         Log.i(K9.LOG_TAG, "Processing " + storedUntaggedResponses.size() + " untagged responses from previous commands for " + getLogId());
                                     untaggedResponses = new ArrayList<ImapResponse>(storedUntaggedResponses);
@@ -2607,10 +2607,10 @@ public class ImapStore extends Store {
             if (K9.DEBUG)
                 Log.d(K9.LOG_TAG, "UIDs for messages needing flag sync are " + flagSyncMsgSeqs + "  for " + getLogId());
 
-            if (flagSyncMsgSeqs.size() > 0) {
+            if (!flagSyncMsgSeqs.isEmpty()) {
                 syncMessages(flagSyncMsgSeqs);
             }
-            if (removeMsgUids.size() > 0) {
+            if (!removeMsgUids.isEmpty()) {
                 removeMessages(removeMsgUids);
             }
         }
@@ -2648,7 +2648,7 @@ public class ImapStore extends Store {
                         ImapMessage message = new ImapMessage("" + uid, ImapFolderPusher.this);
                         messages.add(message);
                     }
-                    if (messages.size() > 0) {
+                    if (!messages.isEmpty()) {
                         pushMessages(messages, true);
                     }
                 }
diff --git a/src/com/fsck/k9/mail/store/LocalStore.java b/src/com/fsck/k9/mail/store/LocalStore.java
index 6131f74c5..d10c20ce7 100644
--- a/src/com/fsck/k9/mail/store/LocalStore.java
+++ b/src/com/fsck/k9/mail/store/LocalStore.java
@@ -892,7 +892,7 @@ public class LocalStore extends Store implements Serializable {
 
             whereClause.append(" )");
         }
-        if (folders != null && folders.size() > 0) {
+        if (folders != null && !folders.isEmpty()) {
             whereClause.append(" AND folder_id in (");
             boolean anyAdded = false;
             for (LocalFolder folder : folders) {
@@ -1786,7 +1786,7 @@ public class LocalStore extends Store implements Serializable {
                 @Override
                 public Void doDbWork(final SQLiteDatabase db) throws WrappedException, UnavailableStorageException {
                     Cursor cursor = null;
-                    if (messages.size() == 0) {
+                    if (messages.isEmpty()) {
                         return null;
                     }
                     try {
diff --git a/src/com/fsck/k9/mail/store/Pop3Store.java b/src/com/fsck/k9/mail/store/Pop3Store.java
index 8f017f870..08c25bd10 100644
--- a/src/com/fsck/k9/mail/store/Pop3Store.java
+++ b/src/com/fsck/k9/mail/store/Pop3Store.java
@@ -506,7 +506,7 @@ public class Pop3Store extends Store {
                     unindexedUids.add(uid);
                 }
             }
-            if (unindexedUids.size() == 0) {
+            if (unindexedUids.isEmpty()) {
                 return;
             }
             /*