Java，正则表达式，去除不需要的字符[后跟，前导，之间]

Question

i need help for an regular expression to strip unwanted characters from an String (in Java). I solved this issue with 4 regular expression following each other. The replace will be called many times [peeks: 50+ times/sec] it and decreases performance. But i think it sure possible with an single expression, so the performance will be increased a little.

The TestString is

"   ! ... my-Cruc i@l_\\/Disp lay.Na#m3 ?;()!    "

The tasks i like to perform with regex

• Remove all leading non-alpha charcters – [Beginning of String]
• Remove all trailing non-alphanumeric characters – [End of String]
• Remove all non-alphanumeric characters(except [_-.]) between

So the result will be

my-Cruil_Display.Nam3

The Problem is the switch between, the built-in patterns Alnum and alpha, depending on position in string (beginning, end) and the exception characters [_-.] between them.

I tried this many times in the last few days, but i do not get it to work. Removing leading non-alpha characters is working with regex

^([^\\p{Alpha}]+)?

But if i append the „between“ it doesnt work longer anything

Removing trailing non-alpha charcter with regex

([^\\p{Alnum}]+$) 

is working , but not im combination with all other regex

One of the last tries are

(^[^\\p{Alpha}]+)?[^\\p{Alnum}\\._-]+([^\\p{Alnum}]+$)

Can anyone help to get this working

Answer 1

You may use

^\P{Alpha}+|\P{Alnum}+$|[^\p{Alnum}_.-]

Java:

s = s.replaceAll("^\\P{Alpha}+|\\P{Alnum}+$|[^\\p{Alnum}_.-]", "");

Or, to make it Unicode aware, add the (?U) flag:

s = s.replaceAll("(?U)^\\P{Alpha}+|\\P{Alnum}+$|[^\\p{Alnum}_.-]", "");

Details

• ^\\P{Alpha}+ - any 1 or more chars other than alphabetic chars at the start of the string
• | - or
• \\P{Alnum}+$ - any 1 or more chars other than alphanumeric chars at the end of the string
• | - or
• [^\\p{Alnum}_.-] - any char other than alphanumeric, _ , . and - chars anywhere in the string

See the regex demo .