Get value from nested list using lambda operators java 8

Question

I am having a Order entity which contains list of items with in it, from that I need to loop list of orders and each order contains list of items, i need to extract Items alone from that items i need to extract single item quantity here my code

public class order{
    private Integer orderId;
    private String orderNo;
    .
    .
    private List<item> items;
    .
    .
    .
}

public class item{
    private Integer itemId;
    private String itemCode;
    private String itemDescription;
    private BigDecimal cost;
    .
    .
    .
}

How to iterate this in java8?

Konstantin Yovkov · Accepted Answer · 2016-08-30 10:43:54Z

2

If you have a:

List<Order> list = ...

you could .flatMap() the nested list(s) of Item objects with:

List<Item> allItems = list.stream()
                          .map(Order::getItems)
                          .flatMap(List::stream)
                          .distinct()
                          .collect(Collectors.toList());

answered Aug 30, 2016 at 10:43

Konstantin Yovkov

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Comments

rorschach · Accepted Answer · 2016-08-30 11:33:37Z

1

Your explanation is confusing.

If you have a single Order with Items that you need to loop over, it's really easy:

Order singleOrder;

singleOrder.getItems().stream()
    .//whatever else you need;

If you have a List of Orders, it's still really easy:

List<Order> multipleOrders;

multipleOrders.stream()
    .map(Order::getItems)
    .flatMap(List::stream)
    .//whatever else you need

edited Aug 30, 2016 at 11:33

answered Aug 30, 2016 at 10:49

rorschach

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