See this page for more details java regular expressions:
https://docs.oracle.com/en/java/javase/23/docs/api/java.base/java/util/regex/Pattern.html

final Pattern pattern = Pattern.compile("^([a-zA-Z]+)? (\\w+)$");

final Matcher matcher = pattern.matcher("ABC _012_");

if (matcher.matches()) {
    final String group1 = matcher.group(1);
    final String group2 = matcher.group(2);

    System.out.println(group1);
    System.out.println(group2);
}