使用正则表达式将冒号添加到 mac 地址

Question

I have a mac address looking like this 482C6A1E593D and I want to return it into something like this 48:2C:6A:1E:59:3D

I have been able to make this code:

Pattern.compile("(.{2})").matcher(macAddress).replaceAll("$1:");

However it returns 48:2C:6A:1E:59:3D: instead of 48:2C:6A:1E:59:3D I would like to ignore the last match to avoid having the last :

Answer 1

You should use a negative look head for end of String.

public static void main(String[] args) {
    String s = "482C6A1E593D";
    s = s.replaceAll("(\\w{2})(?!$)", "$1:");
    System.out.println(s);
}

O/P :

48:2C:6A:1E:59:3D

Answer 2

You may also use a positive lookahead requiring a symbol to be present:

String macAddress = "482C6A1E593D";
System.out.println(macAddress.replaceAll(".{2}(?=.)", "$0:"));

See this demo

Note you do not need any capturing groups here since $0 is a backreference to the whole match (same can be used with TheLostMind's regex - use s.replaceAll("\\\\w{2}(?!$)", "$0:") ).

Answer 3

Kotlin version of Wiktor Stribiżew 's answer:

val macAddress = "482C6A1E593D"
println(macAddress.replace(".{2}(?=.)".toRegex(), "$0:"))