StringBuffer in java

In this program the same characters are seperated by *

public class IDString {

public static void main(String[] args) {

StringBuffer str1=new StringBuffer("hii my naame iisss");
System.out.println("Initially the string is: "+str1);
for(int i=0;i<str1.length()-1;i++)
{
if(str1.charAt(i)==str1.charAt(i+1))
{
str1.insert(i+1,'*');
}
}

System.out.println("String is :"+str1);
}
}