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

[Roger Riggs]

On Tue, 28 Feb 2023 09:05:44 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> 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`.

OOME is used for a number of not-strictly out of memory conditions, for example off-heap allocation and allocations that can't succeed because they exceed implementation limits.

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