on how regular expressions match any character, including line breaks

In Java today, you want to use regular expressions to get any character in a piece of text. So it is very random to write the following matching rules:

(.*)

The result is run and the text after the line break is not found. So I checked the manual and found the regular expression, "." (dot symbol) matches all characters except the newline character "\ n". At the same time, there is a word in the manual: to match any character including ' \ n ', use a pattern like ' [. \ n] '. So I modified the regular expression matching rule as follows:

([. \n]*), of course, if it is written directly in a Java program, it needs to be changed to ([. \\n]*)

The results run the program again and find out what is not being taken. I am baffled, and modify it to the following rules:

([.| \n]*) and ([\ n.] *)

The result is still no, nothing is taken. Looks like the dot symbol and line break Fu Yi retwist ~

And then on the Internet a check, although did not find out what the above rule is a problem, but found a solution, after a try, sure enough to match any character including newline characters, the following is the correct regular expression matching rules :

([\s\s]*)

It can also be expressed as "([\d\d]*)", "([\w\w]*)").