Loop on ArrayNode tranform to stream

I'm trying to use streams() to convert this code. I'm using jackson library.

JsonNode convert(final ObjectNode src)
boolean checkNotEmpty(final JsonNode node)


ArrayNode newArray = mapper.createArrayNode();
for (final JsonNode node: arrayNodes)
JsonNode newNode = convert((ObjectNode) fiwareNode);
if (checkNotEmpty(newNode))
newArray.add(newNode);




Currently I have:

ArrayNode a = StreamSupport.stream(nodes.spliterator(), true)
.map(e -> convert((ObjectNode)e))
.filter(e -> checkNotEmpty(e))
.collect(Collector.of(
mapper.createArrayNode(), // init accumulator
ArrayNode::add, // processing each element
));


However I'm getting:

The type ArrayNode does not defined add(R,T) that is applicable here


Any idea on how to fix it?

Edit:

I found this. Do I have to implement this class? Is it possible to do it inline? So I guess this is going to be the solution ;)

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Collector.of

2 Answers
2

Something like this?

ArrayNode newArray = mapper.createArrayNode();
arrayNodes.stream()
.map(YourClass::convert)
.filter(YourClass::checkNotEmpty)
.forEach(newArray::add);


I know it's not a one-liner, but why bother writing a custom collector?

You can do it like this (ArrayNode has a addAll iirc)

ArrayNode

addAll

arrayNodes.stream()
.map(YourClass::convert)
.filter(YourClass::checkNotEmpty)
.forEach(newArray::add);
.collect( mapper.createArrayNode(),
(l, e) -> l.add(e),
(l1, l2) -> l1.addAll(l2));


You could of course create a new Collector. The one in the link you found just does what you want it to do. This is especially useful when you need this piece multiple times.

Collector

But if you want to just write a single statement — one of the overloaded versions of the collect method in the Stream class accepts a supplier, an accumulator and a combiner. The ObjectMapper class can create an ArrayNode instance through the createArrayNode method, while the ArrayNode class provides add and addAll methods. These are all you need:

collect

Stream

ObjectMapper

ArrayNode

createArrayNode

ArrayNode

add

addAll

ArrayNode newArray = arrayNodes.stream()
.map(t -> convert((ObjectNode) t))
.filter(YourClass::checkNotEmpty)
.collect(mapper::createArrayNode, ArrayNode::add, ArrayNode::addAll);


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