Triplicate all digits in a string

Question

I have a string containing digits like "abc123" and I want every digit to show up 3 times like this: "abc111222333" .

Is there a way to do this with replaceAll("\\\\d+.*", ???) whereas the ? is whatever digit was found?

Respectively, is there anything "better" than this?:

String input = "abc1x23z";
String output = input;

for (int i = 0, j = i; i < input.length(); i++) {
    char c = input.charAt(i);

    if ( Character.isDigit( c ) ) {
        String a = output.substring(0, j+1);
        String b = output.substring(j, output.length());

        output = a + c + b;
        j += 3;
    }else{
        j++;
    }
}

System.out.println(output);     // abc111x222333z

Answer 1

You can use "abc123".replaceAll("(\\\\d)", "$1$1$1")

Explanation:

• \\\\d matches a single digit
• () captures a group
• $1 points to the first group captured by each match of the regex