Java 8 lambda list inside list filter

Question

Sample JSON

[
  {
    "id": "1",
    "products": [
      {
        "id": "333",
        "status": "Active"
      },
      {
        "id": "222",
        "status": "Inactive"
      },
      {
        "id": "111",
        "status": "Active"
      }

    ]
  },
  {
    "id": "2",
    "products": [
      {
        "id": "6",
        "status": "Active"
      },
      {
        "id": "7",
        "status": "Inactive"
      }
    ]
  }
]

I want to retrieve list of objects that have at least one active product.

Below code returns list of products but I want a list of ProdcutResponse. Any way to do this?

 response.stream()
 .map(ProductResponse::getProducts)
 .filter(s -> "Active".equals(s.getType()))
 .collect(Collectors.toList())

Jacob G. · Accepted Answer · 2017-11-25 03:58:50Z

8

Because you didn't show much code, this will be a shot in the dark. My main suggestion would be to not map the Stream<ProductResponse> to a Stream<List<Product>> before collecting it to a list:

response.stream()
        .filter(pr -> pr.getProducts().stream().anyMatch(s -> "Active".equals(s.getType())))
        .collect(Collectors.toList());

You can change anyMatch to allMatch if you want the List<ProductResponse> to contain onlyProducts with active types (whatever that means).

answered Nov 25, 2017 at 3:58

Jacob G.

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1 Comment

Jacob G. Over a year ago

@Forhad The time complexity is O(n^2). Some pre-computation would be required to optimize it.

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