Masking a credit card value

[Samurai Coder]

The following code produces a mask that looks like 4xxx-xxxx-xxxx-1221

We want a mask that is simply the last 4 digits.

How would I modify this code to get that result?

public static String maskNumber(String accno) {
StringBuffer sb = new StringBuffer();
if (StringUtils.isNotBlank(accno)) {
int length = accno.length();
int mask = length;
if (length > 7) {
mask = length - 4;

for (int i = 0; i < mask; i++) {
if (i % 4 == 0) {
sb.append("-");
}
sb.append("x");
}
sb.reverse();
sb.append(accno.substring(mask));
sb.replace(0, 1, String.valueOf(accno.charAt(0)));

} else {
// if account.length too short, do not show length and mark
// as xxxxxN
mask = length - 1;

sb.append("xxxxx");
sb.append(accno.substring(mask));
if (length > 4) {
sb.replace(0, 1, String.valueOf(accno.charAt(0)));
}
}
}
return sb.toString();
}

[xcallmejudasx]

start with the unmasked number. Then add 4, -, 4, -, 4, -, xxxx

I mean essentially copy your unmasked string into a new string builder starting from index 0 and once you hit index[length-5] just put x's

[Samurai Coder]

Thanks. I think thats essentially what I get if I reverse engineer what the previous coder has done. Like so...

public static String maskNumber(String accno) {
StringBuffer sb = new StringBuffer();
if (StringUtils.isNotBlank(accno)) {
int length = accno.length();
int mask = length;
if (length > 7) {
mask = length - 4;

sb.append(accno.substring(mask));


} else {
// if account.length too short, do not show length and mark
// as xxxxxN
mask = length - 1;

sb.append("xxxxx");
sb.append(accno.substring(mask));
if (length > 4) {
sb.replace(0, 1, String.valueOf(accno.charAt(0)));
}
}
}
return sb.toString();
}