Java String ReplaceAll method giving illegal repetition error?

Question

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 "{" ?

Smutty

Answer 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

Vaucluse

Answer 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.

Bilocular

Holy crap... I've been using Groovy for years and always assumed replace() just replaced the first instance. That's what I get for not looking at the docs! – Eyeful

Answer 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).

Brentbrenton