试试这个：

System.out.println(s.replaceAll("<Name1>(.{1,5})(.*)</Name1>", "<Name1>*****$2</Name1>"));

更多说明here

编辑以下是跟踪掩码字符计数的代码：

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexXmlRplc {
    private static Pattern pattern = Pattern.compile("<Name1>(.{1,5})(.*)</Name1>");

    public static void main(String[] args) {
        String s = "<Name1>joe</Name1>";
        mask(s);
        s = "<Name1>Edward Smith</Name1>";
        mask(s);

    }

    private static void mask(String s) {
        Matcher matcher = pattern.matcher(s);
        if (matcher.find()) {
            int length = matcher.group(1).length();
            String replacement = "<Name1>" + "*".repeat(length) + "$2</Name1>";
            System.out.println(matcher.replaceAll(replacement));
        } else {
            System.out.println("No match");
        }
    }
}