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

public class practice {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String regex = "([0-9]+)";
        String example = "99999";

        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(example);

        String tiPrint = matcher.group(0);
        System.out.printf("%s",tiPrint);

    }
}

Exception in thread "main" java.lang.IllegalStateException: No match found
	at java.base/java.util.regex.Matcher.group(Matcher.java:645)
	at practice.main(practice.java:14)

Process finished with exit code 1