为什么在我写replaceAll（“\\p{P}”，“”）时删除“\n”，因为“\\p{P}”只是PUNCTATION的正则表达式

Question

why is "\n" removed when I write replaceAll("\\p{P}", "") , because "\p{P}" is a regular expression for PUNCTATION only. "\n" line break is not a punctuation mark?

For example, after this regular expression, a group of lines

1,2,3
4.5
6.7?8

converted to 12345678

why was the line break removed?

Answer 1

The regex POSIX character class for puncutation ( \p{P} or \p{Punct} ) does not remove line-breaks.

See the demo on IDEone :

String multiline = "1,2,3\n4.5\n6.7?8";
System.out.println(multiline.replaceAll("\\p{P}", ""));

Prints the string with line-breaks preserved:

123
45
678