https://source.android.com/docs/setup/reference/androidbp
and of course for IsMatch there is no difference in which direction you go, you can just stop at the first match and return true. in fact lookarounds aren’t necessary for IsMatch at all, they are indistinguishable from concatenation. a(?=b) is just ab for the purposes of IsMatch and a(?=.*b)(?=.*c) is just a(.*b_*&.*c_*) - the lookarounds only come into play when you want to know the position of the match, and what is around it. if you happen to use lookarounds in an IsMatch pattern today, consider RE# intersections a faster drop-in replacement with identical semantics.
，这一点在PDF资料中也有详细论述
36 years later, my under-13 kid struck up a conversation about the life spans of jellyfish. He said there were immortal species. Skeptical, I pushed back. His confidence didn’t waver because he “did his research.” He was right and I learned about the Turritopsis dohrnii.
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