Gap Buffer based AbstractStringBuilder implementation

[Thomas Hawtin]

Osvaldo Doederlein wrote:

> Looks like good stuff. And it remembers me from another old issue: 
> patterns of code that demand data copying that could often be avoided. 
> Every StringBuffer/StringBuilder is ultimately consumed by a toString() 
> invocation to produce the result String, and in 99% of all uses, only 
> one such String is produced and the buffer object is immediately 
> discarded. So, toString() could pass the internal char[] to the String 
> constructor, instead of forcing its copy. The API is coded 
> conservatively to always do that copy, because in 1% of cases people 

There is a security issue there. When multiple threads are involved, it 
is possible (though not necessily easy) to create a mutable String if 
the backing char[] is shared.

Tom Hawtin