private int parseInteger(Tree node, int def) {
    if (node == null) {
      return def;
    } else {
      return Integer.parseInt(node.getText());
    }
  }
Composes an overlay object.

Output is a flattened view of the input objects.
having the value from the first one which has it defined from the overlays.
ql/src/java/org/apache/hadoop/hive/ql/parse/ScheduledQueryAnalyzer.java