masking a creditcard number in java

Question

I tried to mask the characters in a creditcard number string using character \'X\'.I wrote two functions as below .The second function uses commons.lang.StringUtils

Answer 1

Using Apache StringUtils...

String ccNumber = "123232323767"; 

StringUtils.overlay(ccNumber, StringUtils.repeat("X", ccNumber.length()-4), 0, ccNumber.length()-4);