Iterate nested object in java8

Question

I'm new to java8.
I have the following classes.

class User {
  List<Vehicle> vehicle;
  private int vehiclecount;

  public List<Vehicle> getVehicle() {
        return vehicle;
  }
}

class Vehicle{
  String vehiclename;
  String vehiclecolor;
}

I am able to save this in mongo collection:

{ "_id" : ObjectId("59ca1e53a1a79607fcc9200f"), "_class" : "com.test.User", 
   "vechicle" : [ { "vehiclename" : "Car", "vehiclecolor" : "Blue" } ], 
   "count" : 1, "createdDate" : ISODate("2017-09-26T09:30:59.826Z") }

Now i pulled out the result based on spring mongo data repository. i want to iterate the above mongo collection so that i can only get the vehicle list I tried the below:

List<Vehicle> vehicle = result.stream().filter(vehicles->vehicles.getVehicle().stream().collect(Collectors.toList());

Please help im new to java8. Thanks in advance

`result` is a collection of users? and you want to obtain a collection of vehicles? — Eugene, Sep 27 '17 at 10:31
Possible duplicate of [What is the proper way of replacing a nested for loop with streams in Java 8?](https://stackoverflow.com/questions/27174700/what-is-the-proper-way-of-replacing-a-nested-for-loop-with-streams-in-java-8) — user140547, Sep 27 '17 at 10:44

score 4 · Accepted Answer · edited Jul 28 '18 at 12:23

4

If I understood correctly:

List<Vehicle> vehicles = 
    result.stream()
       .flatMap(user -> user.getVehicle().stream())
       .collect(Collectors.toList());

edited Jul 28 '18 at 12:23

Ousmane D.

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answered Sep 27 '17 at 10:34

Eugene

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works like charm.. Thanks Eugune.. solved the problem. – user24393 Sep 27 '17 at 10:40
sure ..definately. intially i accepted but it asked to wait for some time to accept an answer. – user24393 Sep 27 '17 at 10:43
But when i try to iterate the list vehicles, im getting the entire vehicle object itself (result == com.test.Vehicle@17220255), i want to retrieve vehiclename and vehiclecolor of the vehicle. Below is my code: vehicles.forEach(result->System.out.println("result == "+result)); – user24393 Sep 27 '17 at 11:04
sorry missed to retrieve the properties from result object.vehicles.forEach(result->System.out.println("result == "+result.getvehiclename()+" color>>"+result.getvehiclecolor())); – user24393 Sep 27 '17 at 11:25
is there a way to retrieve the "_id" field from the result stream? – user24393 Sep 27 '17 at 13:17

Iterate nested object in java8

1 Answers1