String replace throws error with $ sign

java, regex, string

Solution

That's because the dollar sign is a special character in a replacement string, use `Matcher.quoteReplacement()` to escape this kind of character.

subject = subject.replaceAll("\\[calEvent\\]", Matcher.quoteReplacement(calSubject));

From the doc of `String.replaceAll()` :

Note that backslashes (`\`) and dollar signs (`$`) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use `Matcher.quoteReplacement(java.lang.String)` to suppress the special meaning of these characters, if desired.

Note that the dollar sign is used to refer to the corresponding capturing groups in the regular expression (`$0`, `$1`, etc.).

EDIT

`Matcher.quoteReplacement()` has been introduced in Java 1.5, if you're stuck in Java 1.4 you have to escape `$` manually by replacing it with `\$` inside the string. But since `String.replaceAll()` would also take the `\` and the `$` as special characters you have to escape them once and you also have to escape all `\` once more for the Java runtime.

("$", "\$") /* what we want */
("\$", "\\\$") /* RegExp engine escape */
("\\$", "\\\\\\$") /* Java runtime escape */

So we get :

calSubject = calSubject.replaceAll("\\$", "\\\\\\$");

Problem

I'm having an issue with replacing a string in java... the line is: ``` subject = subject.replaceAll("\\[calEvent\\]", calSubject); ``` This line doesn’t work with $ sign in calSubject. what the subject variable is, a dynamic subject line variable from a file. for example like so: Calnot = [calEvent] what i am trying to do is replace the calEvent place holder with the subject variable. but how i did it does not work because it crashes when the subject contains a $ sign. any idea how I can do this so it won't break if the subject contains a $ sign or any characters for that matter?

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