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kotlinlang

Hi guys, I'm wondering if the `?.` operator thread safe? for example I have a `var str: String? = null` , is it safe to call `str?.length` ? could NPE happen?

It's equivalent to
```val localStr = str
if (localStr != null) {
  localStr.length
}```

The ‘call’ to `?.`  itself is ‘thread-safe’/‘atomic’.
But afer that call, the global/instance variable you called it on, can be null again.

a `let` on that would resolve the thread safety issue, right?
My understanding is that
```str?.let {
it.length
} ```
would be safe since the `it` is a copy

there is no issue. that code is equivalent to `str?.length`

~Huh, I honestly thought `let` made a local copy. Thanks!~ Right, I see now

It does. So does `str?.length`. That was my point.