findbugs: check the size of a collection against isEmpty() instead of checking against size zero

src/main/java/com/owncloud/android/files/FileMenuFilter.java

@@ -99,7 +99,7 @@ public class FileMenuFilter {
      * @param inSingleFileFragment  True if this is not listing, but single file fragment, like preview or details.
      */
     public void filter(Menu menu, boolean inSingleFileFragment) {
-        if (mFiles == null || mFiles.size() <= 0) {
+        if (mFiles == null || mFiles.isEmpty()) {
             hideAll(menu);
         } else {
             List<Integer> toShow = new ArrayList<>();

src/main/java/com/owncloud/android/jobs/MediaFoldersDetectionJob.java

@@ -98,7 +98,7 @@ public class MediaFoldersDetectionJob extends Job {
             imageMediaFolderPaths.removeAll(mediaFoldersModel.getImageMediaFolders());
             videoMediaFolderPaths.removeAll(mediaFoldersModel.getVideoMediaFolders());
 
-            if (imageMediaFolderPaths.size() > 0 || videoMediaFolderPaths.size() > 0) {
+            if (!imageMediaFolderPaths.isEmpty() || !videoMediaFolderPaths.isEmpty()) {
                 Account[] accounts = AccountUtils.getAccounts(getContext());
                 List<Account> accountList = new ArrayList<>();
                 for (Account account : accounts) {

src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java

@@ -640,7 +640,7 @@ public class ReceiveExternalFilesActivity extends FileActivity
         List<OCFile> tmpFiles = getStorageManager().getFolderContent(mFile, false);
         tmpFiles = sortFileList(tmpFiles);
 
-        if (tmpFiles.size() <= 0) {
+        if (tmpFiles.isEmpty()) {
             return;
         }
         // filter on dirtype
@@ -749,7 +749,7 @@ public class ReceiveExternalFilesActivity extends FileActivity
         if (mFile != null) {
             List<OCFile> files = getStorageManager().getFolderContent(mFile, false);
 
-            if (files.size() == 0) {
+            if (files.isEmpty()) {
                 setMessageForEmptyList(R.string.file_list_empty_headline, R.string.empty,
                         R.drawable.ic_list_empty_upload);
             } else {
@@ -873,8 +873,7 @@ public class ReceiveExternalFilesActivity extends FileActivity
             mStreamsToUpload = intent.getParcelableArrayListExtra(Intent.EXTRA_STREAM);
         }
 
-        if (mStreamsToUpload == null || mStreamsToUpload.size() == 0 ||
-                mStreamsToUpload.get(0) == null) {
+        if (mStreamsToUpload == null || mStreamsToUpload.isEmpty() || mStreamsToUpload.get(0) == null) {
             mStreamsToUpload = null;
             saveTextsFromIntent(intent);
         }

src/main/java/com/owncloud/android/ui/fragment/OCFileListFragment.java

@@ -890,7 +890,7 @@ public class OCFileListFragment extends ExtendedListFragment implements
      * @return 'true' if the menu selection started any action, 'false' otherwise.
      */
     public boolean onFileActionChosen(int menuId, Set<OCFile> checkedFiles) {
-        if (checkedFiles.size() <= 0) {
+        if (checkedFiles.isEmpty()) {
             return false;
         }
 

src/main/java/com/owncloud/android/ui/fragment/contactsbackup/ContactListFragment.java

@@ -716,7 +716,7 @@ class ContactListAdapter extends RecyclerView.Adapter<ContactListFragment.Contac
                 checkedVCards.remove(verifiedPosition);
             }
 
-            if (checkedVCards.size() == 0) {
+            if (checkedVCards.isEmpty()) {
                 EventBus.getDefault().post(new VCardToggleEvent(false));
             }
         }

src/main/java/com/owncloud/android/ui/fragment/contactsbackup/ContactsBackupFragment.java

@@ -244,7 +244,7 @@ public class ContactsBackupFragment extends FileFragment implements DatePickerDi
 
                     Collections.sort(backupFiles, new AlphanumComparator<>());
 
-                    if (backupFiles == null || backupFiles.size() == 0) {
+                    if (backupFiles == null || backupFiles.isEmpty()) {
                         contactsDatePickerBtn.setVisibility(View.GONE);
                     } else {
                         contactsDatePickerBtn.setVisibility(View.VISIBLE);

src/main/java/com/owncloud/android/utils/FilesSyncHelper.java

@@ -254,7 +254,7 @@ public class FilesSyncHelper {
 
     public static void scheduleOfflineSyncIfNeeded() {
         Set<JobRequest> jobRequests = JobManager.instance().getAllJobRequestsForTag(OfflineSyncJob.TAG);
-        if (jobRequests.size() == 0) {
+        if (jobRequests.isEmpty()) {
             new JobRequest.Builder(OfflineSyncJob.TAG)
                     .setPeriodic(TimeUnit.MINUTES.toMillis(15), TimeUnit.MINUTES.toMillis(5))
                     .setUpdateCurrent(false)