[twotwotwo]

I'm saying I think it would take GC rearchitecting for Java to be able use a pointer into the middle of the string in its internal String representation, because Java's GC, unlike Go's, is currently not built such that a pointer into the middle of anything keeps that thing "alive" for GC purposes; you have to have a pointer to the beginning. Sun made that choice that in hopes they could write a faster GC that way, I suspect.

Given that GC design, Go's two-word substring references (pointer into middle of string + count) wouldn't work; even if String were a builtin, with the no-internal-pointers GC design it would need to be at least three words (pointer to start of string, offset, count).

tl;dr of my larger point is--I think Java needed a few extra bytes/String to support substrings by reference because of how its GC works differently from Go's, and I think that explains why Java decided to remove its substring-by-reference trick while Go didn't. (And I'm not trying to say either way is worse, just trying to really grok why they're different.)