java regexp capture or tabs or spaces on start of string

Question

i try to capture tabs or spaces in the group to use them using replace all it can be or space or tab or both and i like to set it group as i like to use it in the string above (Test_me)

This example doesn't work

String content  = "\t\t<image.name>ABCD:44</docker.image.name>\n";
String content2  = "  <image.name>ABCD:44</docker.image.name>\n";
String source = "ABCD:44";
String destination = "${XXXX}";

content = content.replaceAll("(^[ \\s\\t]*)(<image.name>.*" + source + ")(.*?>)",
                            "$1Test_me\n" +
                            "$1" + Matcher.quoteReplacement("<image.name>" + destination) + "$3");

Answer 1

If you want to replace whitespace (space, tab etc.) captured by the first capturing group, (\\\\s*) , you need to omit them (ie $1 ) in the second argument.

Demo:

import java.util.regex.Matcher;

public class Main {
    public static void main(String[] args) {
        String content = "\t\t<image.name>ABCD:44</docker.image.name>\n";
        String content2 = "  <image.name>ABCD:44</docker.image.name>\n";
        String source = "ABCD:44";
        String destination = "${XXXX}";

        content = content.replaceAll("(\\s*)(<image.name>.*" + source + ")(.*?>)",
                "Test_me\n" + Matcher.quoteReplacement("<image.name>" + destination) + "$3");
        System.out.println(content);
    }
}

Output:

Test_me
<image.name>${XXXX}</docker.image.name>