Mask Alternative chars in a String using Regex in java

Question

I need a regex pattern, which can mask alternative 2 chars in a string in java.. But the input string we cannot predict. For Example

String pattern = "abcdefgh";
OutPut: "ab\*\*ef\*\*"

So the expression should be common one. Not specific for the above string

Answer 1

This should work for you :

public static void main(String[] args) {
    String pattern = "abcdefghijklmnop";
    System.out.println(pattern.replaceAll("(\\w{2})(\\w{2})", "$1**"));
}

O/P :

ab**ef**ij**mn**

replaceAll("(\\\\w{2})(\\\\w{2})", "$1**")) ==> Replaces 2 groups 2 chars each with "2 chars,**".

Note that if you have odd chars, the last char will not be masked. This should fix it == > System.out.println(pattern.replaceAll("(\\\\w{2})(\\\\w{2})", "$1**").replaceAll("(\\\\w{2})\\\\w$", "$1*"));