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);
 }

}

Answer 2

I had the same problem, so I end up implementing replace all with split.
It solved the exception for me

public static String replaceAll(String source, String key, String value){
    String[] split = source.split(Pattern.quote(key));
    StringBuilder builder = new StringBuilder();
    builder.append(split[0]);
    for (int i = 1; i < split.length; i++) {
        builder.append(value);
        builder.append(split[i]);
    }
    while (source.endsWith(key)) {
        builder.append(value);
        source = source.substring(0, source.length() - key.length());
    }
    return builder.toString();
}