hello stupid question of the day about this code s...

# announcements

[nfrankel]

hello
stupid question of the day
about this code snippet:
while (shorteneds.putIfAbsent(url, this) != null) {}
of course, intellij complains that the block is empty
any idea how to write a better version without the complaint?
i’m probably missing something from stdlib...

[diesieben07]

while (shorteneds.putIfAbsent(url, this) != null) {
  // intentionally empty
}

[Jurriaan Mous]

while (shorteneds.putIfAbsent(url, this) != null) Unit

[nfrankel]

thanks @diesieben07 @Jurriaan Mous
you were fast!
i prefer the second better as it relies on types

[diesieben07]

The Unit is completely meaningless here, btw.
while (something) Int does the same thing

[nfrankel]

yep
but Int raises my eyebrow
while with Unit i can understand the reason

[natpryce]

Won’t the while busy-loop? It feels like there should be something in the body of the loop to wait for the existing entry to be removed

[jw]

It should probably contain Thread.onSpinWait

[jw]

And that better had be a synchronized collection or you might loop forever!

[nfrankel]

FYI
it’s actually a hazelcast call
and it should loop until it finds no collision

[Cheolho Jeon]

I might try below. even though it creates a longer code but I think it’s more readable.

var result: Any?
do {
    result = shorteneds.putIfAbsent(url)
} while(result != null)

// or

var result = shorteneds.putIfAbsent(url)
while (result != null) {
    result = shorteneds.putIfAbsent(url)
}

because for me the while loop works like while (condition) do {action}. not while(condition - and - action). If you know what I mean..