Java 8 Lambda - filter two ArrayList

Question

I have two lists. The first one is an ID list of regions, the second one is a node list which has nested region objects.

Structure of my nodeList:

....{
 "id": 6412,
 "name": "303000201",
 "description": "desc",
 "organization": {
    "id": 41065,
    "name": "adad",
    "address": null
 },
 "region": {
    "id": 21,
    "name": "Quba rayonu",
    "code": "303"
 },
 "nodeType": {
    "id": "WELL",
    "name": "Quyu",
    "description": null
 },
 "location": {
    "id": 6412,
    "latitude": 41.36735554,
    "longitude": 48.5041245554
 }} ......

And region list:

{
  "regions": ["56", "44"]
}

I must filter my nodeList for region ID. I do it the old way but I want to do it with lambda expressions. How can I do it?

I googled, tried, but it doesn't work :/

result= nodeList.stream()
                .filter(n -> regionIDList.equals(n.getRegion().getId().toString()))
                .collect(Collectors.toList());

Thank you in advance.

Jeffrey Chung · Accepted Answer · 2017-06-10 11:24:21Z

5

Assuming regionIDList is a List, use contains instead of equals:

result = nodeList.stream()
                 .filter(n -> regionIDList.contains(n.getRegion().getId().toString()))
                 .collect(Collectors.toList());

answered Jun 10, 2017 at 11:24

Jeffrey Chung

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3 Comments

Resul Rzaeeff Over a year ago

Thank you once again ;) It works . But still have a little problem . It return result correctly but there are many null objects inside result list after 1500th object :/ Is it make left join ?)) I don;t understand

Resul Rzaeeff Over a year ago

I need to check if Node (n) is not null

Resul Rzaeeff Over a year ago

nodeListFilteredForRegion = nodeList.stream().filter(n -> Objects.nonNull(n)) .filter(n -> regionIDList.contains(n.getRegion().getId().toString())).collect(Collectors.toList()); I have solved

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