Question

编号以0000-9999这种方式自动生成，java类应该怎么写

Answer 1

public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(getNumber(9999));
}
public static String getNumber(int num)
{
num++;
String result = "";
switch ((num+"").length()) {
case 1:
result = "000" + num;
break;
case 2:
result = "0" + num;
break;
case 3:
result = "0" + num;
break;
case 4:
result = "" + num;
break;
// 此处代表编号已经超过了9999，从0重新开始
default:
result = "0000";
break;
}
return result;
}

Answer 2

从0循环到9999，生成的数据最终字符串化，如果字符串长度小于4，前面少几就补几个0

Answer 3

定义一个静态\线程安全的char数组
比如
public static char[] code = {'0','0','0','0'};