On Mon, 10 Apr 2023 04:57:09 GMT, Glavo <d...@openjdk.org> wrote:
>> Tingjun Yuan has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> Add benchmark
>
> If you really don't trust a collection, then we can't do anything.
>
> Can copying the results of `toArray` ensure accuracy and security? It has too
> many possible problems. Maybe the size of the array is wrong, maybe it forgot
> to copy the contents of the collection and all it returns is an array full of
> nulls.
>
> To put it one step further, is its iterator necessarily correct? Perhaps its
> iterator implementation is also incorrect:
>
>
> class BadList implements List<Object> {
> private Object[] array;
>
> // ...
>
> public Iterator<Object> iterator() {
> // crazy implementation
> return new Iterator<Object>() {
> int i = 0;
>
> public boolean hasNext() {
> return Math.random() < 0.5;
> }
>
> public Object next() {
> if (Math.random() < 0.25) {
> array[i++] = null;
> return new Object();
> } else {
> return array[i++];
> }
> }
> };
> }
> }
>
>
> But who cares? Since its implementation is incorrect, it is normal for it to
> suffer for itself. We only need to prevent errors from being leaked to other
> places, rather than defending against all errors.
@Glavo Then why doesn't `ArrayList` trust `toArray()`? If all implementations
behave correctly, then it should return an `Object[]` independent of the
original collection, so `ArrayList` should trust it. Those who doesn't
implement `toArray()` correctly should use these methods at their own risk,
shouldn't they?
This PR modifies a class that is used by nearly every JVM code, so safety is
more important than performance.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/13383#issuecomment-1501402954
