Why does replaceAll fail with “illegal group reference”?

Question

I am in need to replace

\\\\\\s+\\\\$\\\\$ to $$

I used

String s = \"  $$\";
s = s.replaceAll(\"\\\\s+\\\\$\\\\$\",\"$$\"         


        

Answer 1

import java.util.regex.Pattern;
import java.util.regex.Matcher;
public class HelloWorld{

 public static void main(String []args){
 String msg = "I have %s in my string";

    msg = msg.replaceFirst(Pattern.quote("%s"), Matcher.quoteReplacement("$"));
    System.out.println(msg);
 }

}