How to hide half digits of phone number with star format in flutter?

I want to to hide last 7 digits of phone number like below image.

Here, I resolved it by myself

String number="=+911234567890"

String newNumber=number;

String replaceCharAt(String oldString, int index, String newChar) {
       return oldString.substring(0, index) + newChar + oldString.substring(index + 1);
     }


   for(int i=6; i<number.length;i++){
         newNumber = replaceCharAt(newNumber, i, "*") ; 
         print("PHONE_NUMBER_LOOP:$newNumber");

    }

   print("FinalNumber:$newNumber");