@Override
  public int compare(Object o1, Object o2) {
    return ObjectInspectorUtils.compare(o1, objectInspector1, o2, objectInspector2, mapEqualComparer, nullSortOrder);
  }
This class wraps the ObjectInspectorUtils.compare method and implements java.util.Comparator.
serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectComparator.java