unify empty string compare

Signed-off-by: Jens Mueller <tschenser@gmx.de>

src/main/java/com/owncloud/android/datamodel/OCFile.java

@@ -493,7 +493,7 @@ public class OCFile implements Parcelable, Comparable<OCFile>, ServerFileInterfa
     }
 
     public boolean isInConflict() {
-        return etagInConflict != null && !"".equals(etagInConflict);
+        return !TextUtils.isEmpty(etagInConflict);
     }
 
     public boolean isSharedWithMe() {

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

@@ -26,6 +26,7 @@ import android.content.Intent;
 import android.graphics.PorterDuff;
 import android.os.Bundle;
 import android.text.Editable;
+import android.text.TextUtils;
 import android.text.TextWatcher;
 import android.view.KeyEvent;
 import android.view.View;
@@ -204,7 +205,7 @@ public class PassCodeActivity extends AppCompatActivity implements Injectable {
 
     private void onPassCodeEditTextFocusChange(final int passCodeIndex) {
         for (int i = 0; i < passCodeIndex; i++) {
-            if ("".equals(mPassCodeEditTexts[i].getText().toString())) {
+            if (TextUtils.isEmpty(mPassCodeEditTexts[i].getText())) {
                 mPassCodeEditTexts[i].requestFocus();
                 break;
             }

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

@@ -43,6 +43,7 @@ import android.os.Bundle;
 import android.os.Handler;
 import android.os.Looper;
 import android.os.Parcelable;
+import android.text.TextUtils;
 import android.text.format.DateFormat;
 import android.view.LayoutInflater;
 import android.view.Menu;
@@ -750,7 +751,7 @@ public class ReceiveExternalFilesActivity extends FileActivity
         boolean notRoot = mParents.size() > 1;
 
         if (actionBar != null) {
-            if ("".equals(current_dir)) {
+            if (TextUtils.isEmpty(current_dir)) {
                 ThemeUtils.setColoredTitle(actionBar, R.string.uploader_top_message, this);
             } else {
                 ThemeUtils.setColoredTitle(actionBar, current_dir, this);