How does it deals with singular word sentences. e.g. "Welcome"

You can start the stream on 3, no need to test values below that.

Wow I didn't think of reversing the string items right inside the array...

for some reason kata has error in space in the end, so I think we must create special if else for these

if space was at the end, it woudn't work correctly

Both are slow as you can just use math instead of any loop/stream.

Of course you don't NEED to iterate through. It's a really quick solution to a really quick problem, that's why it's good. The Intstream solution takes 1.3s if the input is 1 billion, but since the tests were way smaller, that ain't a problem. If coding a real project, then of course everyone should think twice if their solution is really the most efficient or not. Here it's not necessary.

Sorry
Im new here

Use spoiler flag when posting a solution like that. Otherwise it appears in the homepage discourse.

yes , because it s a string builder object

this was the first thing i tried but im so bad at variable scoping so my code didn t work

Learned something new !

really ? "best practices" to use old fashion way "loop" instead of lambda ? welcome back to 90's....

Nop.
I just run a benchmark to be sure, with smallNumber = 25 and bigNumber = Integer.MAX_SIZE.

Here are the results :

Benchmark Mode Cnt Score Error Units
MultiplesOf3And5Test.withForLoopAndBigNumber avgt 5 2.680 ± 0.055 s/op
MultiplesOf3And5Test.withForLoopAndSmallNumber avgt 5 28.495 ± 4.046 ns/op
MultiplesOf3And5Test.withParallelStreamAndBigNumber avgt 5 1.044 ± 0.184 s/op
MultiplesOf3And5Test.withParallelStreamAndSmallNumber avgt 5 11284.553 ± 1710.007 ns/op
MultiplesOf3And5Test.withStreamAndBigNumber avgt 5 3.013 ± 0.049 s/op
MultiplesOf3And5Test.withStreamAndSmallNumber avgt 5 94.385 ± 3.109 ns/op

(Yes I used warmup steps to remove JIT and CPU bias)

Here are my interpretations :

• The withForLoop and the withStream are very close with small numbers. The difference comes from the stream initialisation.
• The performance converge with BigNumber
• The parallel implem with default thread-pool stream is 2 time better than every other
• The parallel implem with custom thread-pool could be even better
• People should stop throwing performance asumptions without proper benchmark