java正则基本用法

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

public class zhengz {
    public static void main(String[] args) {
        String line = "This order was placed for QT3000 ok?";
        String pattern = "QT(\d+).ok?";
        Pattern r = Pattern.compile(pattern);
        Matcher m = r.matcher(line);
        System.out.println(m.find());
        System.out.println(m.groupCount());
        System.out.println(m.group(1));
        System.out.println(m.replaceFirst("QT8000 ok!"));

    }
}

输出：

true
1
3000
This order was placed for QT8000?