Masking phone number Java

Question

I need to mask the phone number. it may consist of the digits, + (for country code) and dashes. The country code may consist of 1 or more digits. I have created such kind of regular expression to mask all the digits except the last 4:

inputPhoneNum.replaceAll("\\d(?=\\d{4})", "*");

For such input: [phone]

I get this result: +*******5678

However, it doesn't work for such input: [phone] In particular, it returns just the same number without any change. While the desired output is masking all the digits except for the last 4, plus sign and dashes. That is why I was wondering how I can change my regular expression to include dashes? I would be grateful for any help!

Answer 1

Use this regex for searching:

.(?=.{4})

RegEx Demo

Difference is that . will match any character not just a digit as in your regex.

Java code:

inputPhoneNum = inputPhoneNum.replaceAll(".(?=.{4})", "*");

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However if your intent is to mask all digits before last 4 digits then use:

.(?=(?:\D*\d){4})

Or in Java:

inputPhoneNum = inputPhoneNum.replaceAll("\\d(?=(?:\\D*\\d){4})", "*");

(?=(?:\\D*\\d){4}) is a positive lookahead that asserts presence of at least 4 digits ahead that may be separated by 0 or more non-digits.

RegEx Demo 2