On Mon, 10 Apr 2023 03:36:44 GMT, Chen Liang <li...@openjdk.org> wrote:
>> Tingjun Yuan has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> Add benchmark
>
> Nah. I mean like:
>
> public static String join(CharSequence delimiter,
> Iterable<? extends CharSequence> elements) {
> Objects.requireNonNull(delimiter);
> Objects.requireNonNull(elements);
> var delim = delimiter.toString();
> Object[] elems;
> final int size;
> if (elements instanceof Collection<?> c) {
> elems = c.toArray();
> size = elems.length;
> for (int i = 0; i < size; i++) {
> elems[i] = String.valueOf(elems[i]);
> }
> } else {
> elems = new String[elements instanceof Collection<?> c ? c.size()
> : 8]; // or whatever spliterator you decide to use
> size = 0;
> for (CharSequence cs: elements) {
> if (size >= elems.length) {
> elems = Arrays.copyOf(elems, elems.length << 1);
> }
> elems[size++] = String.valueOf(cs);
> }
> }
> return join("", "", delim, elems, size);
> }
> // ...
> static String join(String prefix, String suffix, String delimiter, Object[]
> elements, int size) { // change array type to Object[], cast on access
> elements
@liach I don't think it's safe because `c.toArray()` can return an array that
may be modified by others. In fact, although the specification of
`Collection.toArray()` indicates that the returned array is free to be
modified, nobody actually trusts this contract. They only trust `ArrayList`
which is most widely-used.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/13383#issuecomment-1501368747
