Why doesn't Stream.limit work as expected in this snippet?

Question

List<Integer> integer = Stream.generate(new Supplier<Integer>() {     int i = 0 ;      @Override     public Integer get() {         return ++i;     } }).filter(j -> j < 5)   .limit(10)   // Note the call to limit here   .collect(Collectors.toList()); 

Counter to my expectation, the collect call never returns. Setting limit before filter produces the expected result. Why?

Answer 1

Since there are only 4 elements that pass the filter, limit(10) never reaches 10 elements, so the Stream pipeline keeps generating new elements and feeding them to the filter, trying to reach 10 elements that pass the filter, but since only the first 4 elements pass the filter, the processing never ends (at least until i overflows).

The Stream pipeline is not smart enough to know that no more elements can pass the filter, so it keeps processing new elements.