I have developed a regular expression to identify a block of xml inside a text file. The expression looks like this (I have removed all java escape slashes to make it read easy):
我已经开发了一个正则表达式来识别文本文件中的xml块。表达式看起来像这样（我删除了所有java转义斜杠以使其易于阅读）：
<\?xml\s+version="[\d\.]+"\s*\?>\s*<\s*rdf:RDF[^>]*>[\s\S]*?<\s*\/\s*rdf:RDF\s*>
Then I optimised it and replaced [\s\S]*? with .*? It suddenly stopped recognising the xml.
然后我优化它并替换[\ s \ S] *？用。*？它突然停止识别xml。
As far as I know, \s means all white-space symbols and \S means all non white-spaced symbols or [^\s] so [\s\S] logically should be equivalent to . I didn't use greedy filters, so what could be the difference?
据我所知，\ s表示所有空格符号，\ S表示所有非白色间隔符号或[^ \ s]，因此[\ s \ S]在逻辑上应相当于。我没有使用贪婪的过滤器，那么有什么区别呢？
2 个解决方案
#1
9
The regular expressions . and \s\S are not equivalent, since . doesn't catch line terminators (like new line) by default.
正则表达式。和\ s \ S不等同，因为。默认情况下不会捕获行终止符（如新行）。
According to the oracle website, . matches
根据oracle网站，。火柴
Any character (may or may not match line terminators)
任何字符（可能与行终止符匹配也可能不匹配）
while a line terminator is any of the following:
行终止符是以下任何一种：
- A newline (line feed) character (
'\n'),- 换行符（换行符）（'\ n'），
- A carriage-return character followed immediately by a newline character (
"\r\n"),- 一个回车符后面跟一个换行符（“\ r \ n”），
- A standalone carriage-return character (
'\r'),- 一个独立的回车符（'\ r'），
- A next-line character (
'\u0085'),- 下一行字符（'\ u0085'），
- A line-separator character (
'\u2028'), or- 行分隔符（'\ u2028'）或
- A paragraph-separator character (
'\u2029).- 段落分隔符（'\ u2029）。
The two expressions are not equivalent, as long as the necessary flags are not set. Again quoting the oracle website:
只要未设置必要的标志，这两个表达式就不相同。再次引用oracle网站：
If
UNIX_LINESmode is activated, then the only line terminators recognized are newline characters.如果激活了UNIX_LINES模式，则唯一识别的行终止符是换行符。
The regular expression
.matches any character except a line terminator unless theDOTALLflag is specified.正则表达式。除非指定了DOTALL标志，否则匹配除行终止符之外的任何字符。
#2
2
Here is a sheet explaining all the regex commands.
这是一张说明所有正则表达式命令的表单。
Basically, \s\S will pickup all characters, including newlines. Whereas . does not pickup line terminators per default (certain flags need to be set to pick them up).
基本上，\ s \ S将拾取所有字符，包括换行符。鉴于。默认情况下不接收线路终结器（需要设置某些标志来接收它们）。
#1
9
The regular expressions . and \s\S are not equivalent, since . doesn't catch line terminators (like new line) by default.
正则表达式。和\ s \ S不等同，因为。默认情况下不会捕获行终止符（如新行）。
According to the oracle website, . matches
根据oracle网站，。火柴
Any character (may or may not match line terminators)
任何字符（可能与行终止符匹配也可能不匹配）
while a line terminator is any of the following:
行终止符是以下任何一种：
- A newline (line feed) character (
'\n'),- 换行符（换行符）（'\ n'），
- A carriage-return character followed immediately by a newline character (
"\r\n"),- 一个回车符后面跟一个换行符（“\ r \ n”），
- A standalone carriage-return character (
'\r'),- 一个独立的回车符（'\ r'），
- A next-line character (
'\u0085'),- 下一行字符（'\ u0085'），
- A line-separator character (
'\u2028'), or- 行分隔符（'\ u2028'）或
- A paragraph-separator character (
'\u2029).- 段落分隔符（'\ u2029）。
The two expressions are not equivalent, as long as the necessary flags are not set. Again quoting the oracle website:
只要未设置必要的标志，这两个表达式就不相同。再次引用oracle网站：
If
UNIX_LINESmode is activated, then the only line terminators recognized are newline characters.如果激活了UNIX_LINES模式，则唯一识别的行终止符是换行符。
The regular expression
.matches any character except a line terminator unless theDOTALLflag is specified.正则表达式。除非指定了DOTALL标志，否则匹配除行终止符之外的任何字符。
#2
2
Here is a sheet explaining all the regex commands.
这是一张说明所有正则表达式命令的表单。
Basically, \s\S will pickup all characters, including newlines. Whereas . does not pickup line terminators per default (certain flags need to be set to pick them up).
基本上，\ s \ S将拾取所有字符，包括换行符。鉴于。默认情况下不接收线路终结器（需要设置某些标志来接收它们）。