Mask Characters in a word

[Godwin]

I want to replace some characters in a word with "*". I tried using the StringBuilder  class but I got the error message :

 error: cannot find symbol
                    String test = String.valueOf(builder.replace(1, 2, "*"));
  symbol:   method replace(int,int,String)
  location: variable builder of type StringBuilder

this is what I did:

StringBuilder builder = new StringBuilder(tempWord);
String test = String.valueOf(builder.replace(1, 2, "*"));

I tried using StringUtil class but there is no method to replace a characters by positions. How can I achieve this?

[Shai Almog]

You will need to do something like:

String test = s.substring(0, 1) + "*" + s.substring(2, s.length());