I am trying to convert below for-loop to forEach method with help Stream function using Java1.8, but I was messed up and also confused to do that.
List<A> valueList = new ArrayList<>();
List<B> responseList = getResponses();
List<A> value = new ArrayList<>();
for (B getResponse: responseList) {
valueList = getValues(getResponse);
value.addAll(valueList);
}
With streams you generally want to avoid creating empty lists and then adding items. Streams should use functional idioms and avoid side effects as much as possible. It's better to work with the stream as a whole and then "collect" the results into a list at the end.
List<C> value = getResponses().stream()
.flatMap(r -> getValues(r).stream())
.collect(Collectors.toList());
I am trying to convert below for-loop to forEach method with help Stream function using Java 1.8.
You shouldn't use a stream along with forEach simply to accumulate into a predefined list as there will be side effects (which should be avoided when dealing with streams), rather go with the stream approach suggested by John Kugelman if you want to perform it with streams or using the forEach method it can also be done as:
List<A> value = new ArrayList<>();
responseList.forEach(response -> value.addAll(getValues(response))));
It appears you are trying to add all the values in responseList to valueList and I think you could just do valueList.addAll(responseList); and not have to use a for loop at all.
You could have a problem though if type B doesn't inherit from A because you can't have a list of two unrelated types.
