code: static String getDataSourceClassName(Collection<String> fileNames) {
  
          for (Map.Entry<String, String[]> entry : classNamesByKey.entrySet())
              if (contains(fileNames, entry.getKey())) {
                  String[] classNames = entry.getValue();
                  return classNames == null ? null : classNames[0];
              }
  
          return null;
      }
docs: Infer the vendor implementation class name for javax.sql.DataSource based on the JAR or ZIP names.
  A best effort is made for the known vendors.
  
  @param fileNames all upper case names of JAR and/or ZIP files for the JDBC driver.
  @return name of the vendor implementation class for javax.sql.DataSource. Null if unknown.