Java Regular Expression : Need Simpler Solution

Question

I am new to regular expressions. I have a string named encryptId (does not contain |) and I want to append the | character after every 20 characters of this string, using the encryptId.replace/replaceAll(Regex,Pattern) function in Java. But it should never have \ at the end of the string.

Thanks for your help.

EDIT:

1. The reason I want to use replace and replaceAll functions particularly is because I have to use that in velocity template mananger. And there we can use common String functions but can't write whole java code.

2. My current solution is shown below

encryptId = encryptId.replaceAll("(.{20})","$1|");
if(encryptId.charAt(encryptId.length() - 1)=='|') {
    encryptId = encryptId.substring(0,encryptId.length()-1);
}

I need to get rid of this if statement so that It would be just a string function.

Answer 1

This can be done via regular expressions as follows

static String enterADelimiter(String str, String delimiter, int after) {
        String regex = "(.{" + after +"})(?!$)";
        String replacement = "$1" + delimiter;

        return str.replaceAll(regex, replacement);
    }

Just use

enterADelimiter(yourString, "|", 20)

This will return correct solution. Explantion

(            Start group 1
  .          Match Anything
  {after}    after times
)            End group 1
(?!$)        Don't match if at end of String