有人可以给一个批注吗

import java.util.Arrays;
import java.util.Scanner;
import java.util.regex.Pattern;
public class Test {
public static void main(String[] args) {
    

    String[] keyWords = new String[]{"class", "interface", "public", "extends", "private", "protect", "while", "if", "for", "abstract", "final"};
    
    Scanner sc = new Scanner(System.in);
    boolean flag = true;
    while(flag) {
        System.out.print("Enter a variable name (q to quit):");
        String str = sc.nextLine();
        if("q".equals(str)) {
           
            flag = false;
            break;
        }
        if("".equals(str) || str == null) {
            System.out.println("legal");
        }else {
            
            String rexOne = "[a-zA-Z]";
            String rexTwo = "[0-9]";
            String rexThree = "[_$]";
            String rexFour = "[a-z]";
            if(str.replaceAll(rexOne, "").replaceAll(rexTwo, "").replaceAll(rexThree, "").length() > 0) {
               
                System.out.println("legal，but uses poor style");
            }else {
               
                String firstStr = str.substring(0, 1);
                if(Pattern.compile(rexTwo).matcher(firstStr).find()) {
                    System.out.println("legal，but uses poor style");
                }else if(Arrays.asList(keyWords).contains(str)){
                    System.out.println("legal，but uses poor style");
                }else {
                    if(str.replaceAll(rexOne, "").replaceAll(rexTwo, "").length() == 0 && Pattern.compile(rexFour).matcher(firstStr).find()) {
                        System.out.println("professional");
                    }else {
                        System.out.println("legal");
                    }
                }
            }
        }
    }
    
}