code: public static boolean checkStorageAccessPermissions(Context context)
      {   //Only for Android M and above.
          if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
              String permission = "android.permission.READ_EXTERNAL_STORAGE";
              int res = context.checkCallingOrSelfPermission(permission);
              return (res == PackageManager.PERMISSION_GRANTED);
          }
          else
          {   //Pre Marshmallow can rely on Manifest defined permissions.
              return true;
          }
      }
docs: Post Lollipop Devices require permissions on Runtime (Risky Ones), even though it has been
  specified in the uses-permission tag of manifest. checkStorageAccessPermissions
  method checks whether the READ EXTERNAL STORAGE permission has been granted to
  the Application.
  @return a boolean value notifying whether the permission is granted or not.