@Override
    public boolean equals(Object o) {

        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        if (!super.equals(o)) {
            return false;
        }

        AbsentStreamStateElement that = (AbsentStreamStateElement) o;

        return waitingTime != null ? waitingTime.equals(that.waitingTime) : that.waitingTime == null;
    }
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