Replace substring (replaceAll) workaround

Question

I'm trying to replace a substring that contains the char "$". I'd be glad to hear why it didnt works that way, and how it would work.

Thanks, user_unknown

public class replaceall {
    public static void main(String args[]) {
        String s1= "$foo - bar - bla";
        System.out.println("Original string:\n"+s1);
        String s2 = s1.replaceAll("bar", "this works");
        System.out.println("new String:\n"+s2);
        String s3 = s2.replaceAll("$foo", "damn");
        System.out.println("new String:\n"+s3);
    }

}

Answer 1

Java's .replaceAll implicitly uses Regex to replace. That means, $foo is interpreted as a regex pattern, and $ is special in regex (meaning "end of string").

You need to escape the $ as

String s3 = s2.replaceAll("\\$foo", "damn");

if the target a variable, use Pattern.quote to escape all special characters on Java ≥1.5, and if the replacement is also a variable, use Matcher.quoteReplacement.

String s3 = s2.replaceAll(Pattern.quote("$foo"), Matcher.quoteReplacement("damn"));

On Java ≥1.5, you could use .replace instead.

String s3 = s2.replace("$foo", "damn");

Result: http://www.ideone.com/Jm2c4