@Override
  public String getDisplayString(String[] children) {
    assert (children.length == 2);
    return "(" + children[0] + " " + opDisplayName + " " + children[1] + ")";
  }
Base class for binary operators, overrides getDisplayString()
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFBaseBinary.java