为什么replaceAll引发异常

Question

i have a string where i want to get rid of brackets

this is my string "(name)" and i want to get "name"

the same thing without the brackets

i had String s = "(name)";

i wrote

s = s.replaceAll("(","");
s = s.replaceAll(")","");

and i get an exception for that

Exception in thread "main" java.util.regex.PatternSyntaxException: Unclosed group near index 1
(

how do i get rid of the brackets?

Answer 1

Parenthesis characters ( and ) delimit the bounds of a capturing group in a regular expression which is used as the first argument in replaceAll . The characters need to be escaped.

s = s.replaceAll("\\(","");
s = s.replaceAll("\\)","");

Better yet, you could simply place the parenthesis in a character class to prevent the characters being interpreted as meta-characters

s = s.replaceAll("[()]","");

Answer 2

s = s.replace("(", "").replace(")", "");

Regex isn't needed here.

If you wanted to use Regex (not sure why you would) you could do something like this:

s = s.replaceAll("\\\\(", "").replaceAll("\\\\)", "");

The problem was that ( and ) are meta characters so you need to escape them (assuming you want them to be interpreted as how they appear).

Answer 3

String#replaceAll takes regular expression as argument. You are using Grouping Meta-characters as regular expression argument.That is why getting error.

Meta-characters are used to group, divide, and perform special operations in patterns.

\       Escape the next meta-character (it becomes a normal/literal character)
^       Match the beginning of the line
.       Match any character (except newline)
$       Match the end of the line (or before newline at the end)
|       Alternation (‘or’ statement)
()      Grouping
[]      Custom character class

So use
1. \\\\( instead of (
2. \\\\) instead of )

Answer 4

You'll need to escape the brackets like this:

s = s.replaceAll("\\(","");
s = s.replaceAll("\\)","");

You need two slashes since the regex processing engine would need to see a \\( to process the bracket as a literal bracket (and not as part of the regex expression), and you'll need to escape the backslash so the regex engine would be able to see it as a backslash.

Answer 5

You need to escape the ( and the ) they have special string literal meaning. Do it like this:

s = s.replaceAll("\\(","");
s = s.replaceAll("\\)","");

Answer 6

s=s.replace("(","").replace(")","");