replaceAll("\\<.?>") vs replaceAll("<.?>")

Question

When using angle brackets in Java regex, what is difference between "\\<" and just "<"?

When I tested, the result was same(or I might miss some cases).

If they are same, why people add "\\" redundantly? Like this or this?

Note: I'm not asking how I can remove HTML from string, so please don't recommend me like JSoup or JTidy.

[Even Jon Skeet cannot parse HTML using regular expressions.](http://stackoverflow.com/a/1732454/963076) — ryvantage, Dec 27 '13 at 05:16

score 5 · Accepted Answer · answered Dec 27 '13 at 05:05

5

The angle-bracket characters can technically be used for lookahead and lookbehind captures, so it can make sense to quote them defensively if the pattern is adding any segments that are provided at runtime.

answered Dec 27 '13 at 05:05

I don't see how this could be an issue. From your link (Java API) it looks like the only times when ``, `(?X)` and lookbehind (`(?<=X)` and `(? – David Knipe Dec 27 '13 at 13:24
@DavidKnipe Have you heard of injection attacks? What if `myString` is what contains the magic opening bit? – chrylis -cautiouslyoptimistic- Dec 27 '13 at 18:45
Yes I do. And I realise that `Pattern.compile("(?" + myString + ")")` is dodgy. But my point is that it's a piece of code that no one would want to use anyway, even ignoring security. To be any use, the first character of `myString` would have to be a special character. The writer of that snippet would be expecting `myString` to begin with ` – David Knipe Dec 27 '13 at 20:31

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