Create a finite stream with a generator function

Question

I have a program to read data from multiple sources, use a tournament tree to merge sort them, pack the data into blocks and output the blocks. I have implemented this as a function, which returns null when no more block is available.

DataBlock buildBlock()

Now I want to output a stream of blocks, but the only method I have found so far is Stream.generate which generates an infinite stream. My stream is of course not infinite. What is a proper way to generate a finite stream from this function?

You can `limit` it. But that depends on the source of your stream. — Naman, Oct 19 '19 at 16:18
You are right. I do not know the actual amount of data until I can read no more from the source, so I have no idea in advance how many blocks to limit — Harper, Oct 19 '19 at 16:19
You seem to be looking for a [while loop equivalent of streams?](https://stackoverflow.com/questions/44700006/is-there-java-stream-equivalent-to-while-with-variable-assignment) — Naman, Oct 19 '19 at 16:42

score 0 · Answer 1 · answered Oct 19 '19 at 18:37

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If you use at least Java 9, you can apply takeWhile(Objects::nonNull) on your stream. If you use the older Java version, check out this question.

answered Oct 19 '19 at 18:37

IlyaMuravjov

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Create a finite stream with a generator function

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