Recursion-Duplicate character formatting

My 2nd testcase is not passing.I have tried HARD.
import java.util.Scanner;

public class Main {

public static void main(String[] args) {
	
	Scanner scn=new Scanner(System.in);
	String str=scn.nextLine();
	scn.close();
	int i=0;
	int e=str.length()-1;
	System.out.println(Removedup(str,i,e));
}

private static String Removedup(String str,int i,int e) {
	
	if(i>=e) {
		return str;
	}
	if(str.charAt(i)==str.charAt(i+1)) {
		str=str.substring(0,i+1)+'*'+str.substring(i+1);
		} 
	
	return Removedup(str,i+1,e);
	
}

}