RFR: JDK-8302323 Add repeat methods to StringBuilder/StringBuffer [v3]

[John Hendrikx]

On Tue, 28 Feb 2023 07:43:13 GMT, Tagir F. Valeev <tvaleev at openjdk.org> wrote:

>> Jim Laskey has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Optimize for empty CharSequence
>
> src/java.base/share/classes/java/lang/AbstractStringBuilder.java line 1903:
> 
>> 1901:             throw new OutOfMemoryError("Required length exceeds implementation limit");
>> 1902:         }
>> 1903:         int total = count * length;
> 
> We may avoid division if we use the long type:
> 
> 
> long totalLong = ((long) count) * length;
> if (totalLong > Integer.MAX_VALUE - offset) {
>     throw new OutOfMemoryError("Required length exceeds implementation limit");
> }
> int total = (int) totalLong;
> 
> 
> Should be faster.

I'm a bit surprised this (and the original code) is throwing `OutOfMemoryError` when running into the max array size. It is not truly an out of memory error, but being an `Error`, it would evade standard catch `Exception` blocks.  I would think this is more of an `IllegalStateException` or perhaps something array specific.

`OutOfMemoryError` is documented pretty specifically that an object allocation failed after exhaustive GC, but no allocation or GC happened:

>Thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.

... which is not happening here at all. This leads me to believe the error is not used correctly here.

Other reasons I find it surprising: `StringBuilder` is not documented to throw this anywhere, it seems to just leak through from various methods implemented by `AbstractStringBuilder`.

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PR: https://git.openjdk.org/jdk/pull/12728