<i18n dev> RFR: JDK-8326908: DecimalFormat::toPattern throws OutOfMemoryError when pattern is empty string

[Justin Lu]

On Sun, 3 Mar 2024 05:00:36 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Please review this PR and corresponding CSR which prevents an OutOfMemoryError by restricting the initial maximum fraction digits for an empty pattern DecimalFormat.
>> 
>> For an empty String pattern DecimalFormat, the maximum fraction digits is initialized to `Integer.MAX_VALUE`. When toPattern() is invoked, StringBuilder internally doubles capacity attempting to append Integer.MAX_VALUE digits until OOME occurs. CSR covers potential behavioral compatibility changes.
>
>> When toPattern() is invoked, StringBuilder internally doubles capacity attempting to append Integer.MAX_VALUE digits until OOME occurs.
> 
> It seems a bug in `toPattern` or `StringBuilder`? May be better to investigate more about it.

Hi @lgxbslgx,

For clarification, this is entirely a bug with DecimalFormat, not StringBuilder. An empty String pattern DecimalFormat sets the maximum fraction digits to `Integer.MAX_VALUE`. When toPattern() is invoked, the local StringBuilder will append until an OOME is thrown by the StringBuilder as there is not enough memory, when internally, the buffer is doubled for a value too large. But such an OOME would occur for any large enough value, so the issue lies with DecimalFormat.

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PR Comment: https://git.openjdk.org/jdk/pull/18094#issuecomment-1977712428