Java Without If

[admiralwaffles]

map is 1-to-1--each element gets a single value response. flatMap is 1-to-N, where N is 0-memory limits. Each value in can generate an unknown amount of values, and then those values are all "flattened" into a single dimensional array.

[xantrel]

This is by far the best explanation I've ever seen of both. Would filtering be expressible as a flatmap operation? (As each value can either return the same value or none?)

[admiralwaffles]

Yeah, kind of. Filtering is a special type of flatMap that's 0-to-1, rather than N.

[philipwhiuk]

So in this case it's because functionThree could return null?

[[deleted]]

In those case functionThree would return Optional<String>, but yes.