For example, Instream.range(0,10) - is iterating from 0 index to 10.
Instream.range(10,0) - but from 10 to 0 is not working, how to do it using Stream API?
- 1Does this answer your question? Java 8 stream reverse orderApokralipsa– Apokralipsa2022-01-08 12:18:36 +00:00Commented Jan 8, 2022 at 12:18
- @Apokralipsa If possible, I would recommend to avoid sorting in this circumstance since sorting is a stateful operation.Turing85– Turing852022-01-08 12:21:15 +00:00Commented Jan 8, 2022 at 12:21
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5 Answers
You can use IntStream.iterate(initialValue, hasNext, next):
IntStream.iterate(10, i -> i >= 0, i -> i - 1) If you are stuck with java 8:
IntStream.iterate(10, i -> i - 1).limit(11) 
1 Comment
user16320675
I recommend
i-1 instead of --iYou cannot generate descending stream using range(). Java doc clearly specifies that the steps are an increment of 1. If there was an option to provide a step then we could have. However, there are different ways in which you can achieve the same.
IntStream.iterate(10, i -> i >= 1, i -> --i) IntStream.rangeClosed(1, 10).boxed().sorted(Comparator.reverseOrder()) IntStream.range(-10, 0).map(i -> -i) Out of this three using and iterate method would be the best approach.
If you want the same set of numbers to be repeated if start/end are transposed then this will replace the ranges if start > end:
IntStream range(int start, int end) { return start < end ? IntStream.range(start,end) : IntStream.range(-start+1, -end+1).map(i -> -i); } range(2,5).forEach(System.out::println); 2 3 4 range(5,2).forEach(System.out::println) 4 3 2 If you want the meaning of (startInclusive, endExclusive) to be preserved modify as:
IntStream range2(int start, int end) { return start < end ? IntStream.range(start,end) : IntStream.range(-start, -end).map(i -> -i); } range2(5,2).forEach(System.out::println) 5 4 3 
Comments
Another trade-off solution is modify the range value like :
int exclusiveEnd = 10; IntStream.range(0, exclusiveEnd).forEach((i) -> { System.out.println(exclusiveEnd - 1 - i); }); 
Comments
Use map after range to calculate new value:
IntStream.range(0, 10).map(i -> 10 - i); // 10, 9, .. 1 IntStream.rangeClosed(0, 10).map(i -> 10 - i); // 10, 9, .. 0