Hazelcast Jet vs Java 8 streams

I'm trying sort List<Map<String,Object>> object based on max date using Hazelcast Jet.

Here is my java 8 code that works:

public static List<Map<String, Object>> extractDate1(List<Map<String, Object>> data) {
    return data.stream().map(value -> new Object() {
        Map<String, Object> theMap = value;
        LocalDate date = extractDate(value);
    }).sorted(Comparator.comparing(obj -> obj.date)).map(obj -> obj.theMap).collect(Collectors.toList());
}

public static LocalDate extractDate(Map<String, Object> value) {
    DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("dd-MM-yyyy");
    DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d-MM-yyyy");
    return LocalDate.parse(LocalDate.parse(value.get("effectiveDate").toString(), formatter2).format(formatter1),
            formatter);
}

The above java 8 code sorts the map objects from low to high:

Below is the Jet code that I'm trying to extract also giving proper output. But I just want to make use of hazelcast jet aggregate/rolling functions

// fetching jsonb type data from db
BatchStage<Object> jobJson = dbValue
        // this model holds the string json value
        // converting json data to Map object
        .map(model -> JsonUtil.mapFrom(model.getJosnValue())
    .filter(map -> map.size() != 0)
    .map(map -> {
            // each json/map object will be having an array and again an array will I have multiple json objects in the
            // I'm filtering json objects based on max date 
      List<Map<String, Object>> extractedDateValue;
            if (map.containsKey("records")) {
         //Here I'm calling external function (above java 8 code)
                 extractedDateValue = extractMapBasedOnMax(
                        (List<Map<String, Object>>) map.get("records"));
            }
                
            return extractedDateValue.get(extractedDateValue.size() - 1);
        });

JSON data example:

{
    "id": "01",
    "records": [{
        "location": "xyz1",
        "effectiveDate": "02-03-2021"
    }, {
        "location": "xyz2",
        "effectiveDate": "02-04-2021"
    }]
}

Expeceted Output:

{
  "location": "xyz2",
   "effectiveDate": "02-04-2021"
}

Is it possible to achieve this through Hazelcast Jet rolling aggregations? Or any suggestions would be helpful.. Thanks

Consider flatMapping the pipeline and finding the maximum using topN. flatMap would convert each JSON structure to series of [id, location, effectiveDate] records. See the documentation of flatMap for code sample.

It's not clear whether you want to find max element in the whole collection or max element per id. Adding a groupingKey would find maximum per id.

The pipeline shape in a "metacode":

source // stream of JSON structures
.flatMap // stream [id, location, effectiveDate]
.groupingKey // for maximum per id, remove for global max
.aggregate(AggregateOpperations.topN) // finds max 
.sink;