Simple Code In Java That Replace All Tabs User Input With Asterisk

I am creating a simple code in Java that replaces all tabs the user inputs with '*'. However, I am doing something wrong and I am not sure what. Here is what I have so far in Eclipse..

import java.util.Scanner; 
public class ReplacingTabs {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String s = "";
String s2 = "";
 
[Code] .....

There is an error with the s2 in the line String s2 = s.replace(' ','*');

I think I need to add String s2 to the loop but I am not sure how..