@Override
    public int hashCode() {

        int result = super.hashCode();
        result = 31 * result + (waitingTime != null ? waitingTime.hashCode() : 0);
        return result;
    }
Absent state element used in pattern to handle not operations.
modules/siddhi-query-api/src/main/java/io/siddhi/query/api/execution/query/input/state/AbsentStreamStateElement.java