如有不足，请可耐的板栗及时提出！
public static void main(String[] args) {//第一题Scanner scanner=new Scanner(System.in);String name=scanner.nextLine();if(name.matches(".*\d.*")) {System.out.println("有数字，不符合标准");}else {System.out.println("用户名没有包含数字");if(name.length()>6) {System.out.println("且长度大于6，用户名创建成功！");}}}
public static void main(String[] args) throws ParseException {//第二题Scanner scanner=new Scanner(System.in);SimpleDateFormat rqzh=new SimpleDateFormat("yyyy-MM-dd");System.out.print("请输入年龄:");String ageString=scanner.nextLine();System.out.print("请输入分数:");String fString=scanner.nextLine();System.out.print("请输入入学日期:");String rqString=scanner.nextLine();Integer age=Integer.valueOf(ageString);Double fs=Double.valueOf(fString);Date rq= rqzh.parse(rqString);System.out.println("年龄为:"+age+" 分数:"+fs+" 入学日期:"+rq);}
public static void main(String[] args) {int a=new Random().nextInt(3);switch(Hld.values()[a]) {case RED:System.out.println("红");break;case YELLOW:System.out.println("黄");break;case GREEN:System.out.println("绿");break;}}enum Hld{RED,YELLOW,GREEN}