问题:

I have a string and when I try to run the replaceAll method, I am getting this strange error:

String str = "something { } , op";
str = str.replaceAll("o", "\n"); // it works fine
str = str.replaceAll("{", "\n"); // does not work

and i get a strange error:

Exception in thread "main" java.util.regex.PatternSyntaxException:
Illegal repetition {

How can I replace the occurrences of "{" ?

回答1:

A { is a regex meta-character used for range repetitions as {min,max}. To match a literal { you need to escape it by preceding it with a \\:

str = str.replaceAll("\\{", "\n"); // does work

回答2:

If you really intend to replace single characters and not regexes (which is what you seem to want to do here), you should use .replace(), not .replaceAll(). In spite of its name, .replace() will replace ALL occurrences, not just the first one.

And in case you wonder, String implements CharSequence, so .replace("{", "\n") will work.

回答3:

Escape it:

str = str.replaceAll("\\{", "\n");

This is needed since the first argument to replaceAll() is a regular expression, and { has a special meaning in Java regular expressions (it's a repetition operator, hence the error message).