简单的猜数字小游戏

public class GuessNumber {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss E");
        String nowTime = sdf.format(date);
        
        /*第一位不能是0,是0就退出游戏*/
        String userRegex = "[1-9][\\d]+";    
        
        System.out.println("请输入您想挑战的0~最大数范围");
        String userScan = scan.next();
        /*判断用户输入的数字是否满足要求*/
        if(userScan.matches(userRegex)){
            int num = Integer.parseInt(userScan);
            guessGame(num);
        }else{
            /*游戏结束时间*/
            System.out.println("取值范围非法,无法开始游戏,再见");
            System.out.println("游戏结束时间:"+nowTime);
        }
    }

    public static void guessGame(int num) {
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss E");
        String nowTime = sdf.format(date);
        Scanner scan = new Scanner(System.in);
        Random rand = new Random();

        int count = 0;    //计数器
        int guessNum = rand.nextInt(num);
        System.out.println("系统已经生成完毕");
        
        long startTime = System.currentTimeMillis();
        System.out.println("请输入您猜测的数字(0退出):");
        int scanNum = scan.nextInt();
        
        while(scanNum != guessNum){
            if(scanNum == 0){
                break;
            }else if(scanNum > guessNum){
                count++;
                System.out.println("不好意思,猜大了,请继续输入");
                scanNum = scan.nextInt();
            }else if(scanNum < guessNum){
                count++;
                System.out.println("不好意思,猜小了,请继续输入");
                scanNum = scan.nextInt();
            }
        }
        if(scanNum == 0){
            System.out.println("遗憾退出,欢迎再来");
            System.out.println("游戏结束时间:"+nowTime);
        }else{
            long endTime = System.currentTimeMillis();
            long totalTime = (endTime - startTime)/1000;
            
            System.out.println("恭喜,您用了"+count+"次猜对了!");
            System.out.println("您的总用时:"+totalTime+"秒");
            System.out.println("游戏结束时间:"+nowTime);
        }
    }
}