@SuppressFBWarnings(value = "MS_EXPOSE_REP", justification = "intended")
  public static HadoopShims getHadoopShims() {
    if (hadoopShims == null) {
      synchronized (ShimLoader.class) {
        if (hadoopShims == null) {
          try {
            hadoopShims = loadShims(HADOOP_SHIM_CLASSES, HadoopShims.class);
          } catch (Throwable t) {
            LOG.error("Error loading shims", t);
            throw new RuntimeException(t);
          }
        }
      }
    }
    return hadoopShims;
  }
Factory method to get an instance of HadoopShims based on the
version of Hadoop on the classpath.
shims/common/src/main/java/org/apache/hadoop/hive/shims/ShimLoader.java