use synchronized

Author: VinayGuthal

firebase-installations/src/main/java/com/google/firebase/installations/local/PersistedInstallation.java

@@ -95,29 +95,31 @@ private File getDataFile() {
         }
       }
     } else {
-      try {
-        String noBackUpFilePath =
-            firebaseApp.getApplicationContext().getNoBackupFilesDir().getCanonicalPath();
-        if (dataFile.getCanonicalPath().startsWith(noBackUpFilePath)) {
-          return dataFile;
-        } else {
-          // Move the file to the no back up directory.
-          File dataFileNonBackup =
-              new File(
-                  firebaseApp.getApplicationContext().getNoBackupFilesDir(),
-                  SETTINGS_FILE_NAME_PREFIX + "." + firebaseApp.getPersistenceKey() + ".json");
-
-          if (!dataFile.renameTo(dataFileNonBackup)) {
-            Log.e(
-                TAG,
-                "Unable to move the file from back up to non back up directory",
-                new IOException("Unable to move the file from back up to non back up directory"));
+      synchronized (this) {
+        try {
+          String noBackUpFilePath =
+              firebaseApp.getApplicationContext().getNoBackupFilesDir().getCanonicalPath();
+          if (dataFile.getCanonicalPath().startsWith(noBackUpFilePath)) {
+            return dataFile;
           } else {
-            dataFile = dataFileNonBackup;
+            // Move the file to the no back up directory.
+            File dataFileNonBackup =
+                new File(
+                    firebaseApp.getApplicationContext().getNoBackupFilesDir(),
+                    SETTINGS_FILE_NAME_PREFIX + "." + firebaseApp.getPersistenceKey() + ".json");
+
+            if (!dataFile.renameTo(dataFileNonBackup)) {
+              Log.e(
+                  TAG,
+                  "Unable to move the file from back up to non back up directory",
+                  new IOException("Unable to move the file from back up to non back up directory"));
+            } else {
+              dataFile = dataFileNonBackup;
+            }
           }
+        } catch (IOException e) {
+          Log.e(TAG, "Error copying data file to non back up directory", e);
         }
-      } catch (IOException e) {
-        Log.e(TAG, "Error copying data file to non back up directory", e);
       }
     }