code: public static String getStoreTypeByFileName(File _file) {
  
          String ext = SystemUtil.getFileExtension(_file.getName()).toLowerCase();
          switch (ext) {
              case STORETYPE_JKS:
              case STORETYPE_PKCS12:
              case STORETYPE_DER_ENCODED:
              case STORETYPE_JCEKS:
                  return ext;
              default:
                  return STORETYPE_JKS;
          }
      }
docs: Get the key/trust store 'type' by analyzing the filename extension.
  
  @param _file file
  @return store type as string, defaults to JKS