java regex escape sequences -


i wondering regex in java , stumbled upon use of backslashes. instance, if wanted occurences of words "this regex" in text, this:

pattern.compile("this regex");

nonetheless, this:

pattern.compile("this\\sregex");

my question is: difference between 2 of them? , why have type backslash twice, mean, why isn't \s escape sequence in java? in advance!

  1. \s means whitespace character, including tab, line feed , carriage return.
  2. java string literals use \ escape special characters. put character \ in string literal, need write "\\". regex patterns use \ escape character, , way put string literal use two, because goes through 2 separate escaping processes. if read regex pattern plain text file example, won't need double escaping.

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