睡不着，写了个数羊小程序

最多数99999只羊，数多了电脑也累

import java.util.HashMap;
import java.util.Map;

public class CountingSheep {

    private static String[] units = {"","十","百","千","万"};
    private static Map<Integer,String> numMap = new HashMap<>();

    static {
        numMap.put(1,"一");
        numMap.put(2,"二");   numMap.put(3,"三");
        numMap.put(4,"四");   numMap.put(5,"五");
        numMap.put(6,"六");   numMap.put(7,"七");
        numMap.put(8,"八");   numMap.put(9,"九");
    }

    private String readAs(int num) {
        if(num >= 100000) return "羊太多了";
        if(num >= 10 && num < 20) {
            if(num == 10) return "十";
            else {
                return "十" + numMap.get(num % 10);
            }
        }
        StringBuilder res = new StringBuilder();
        int indexOfUnits = 0;
        while (num > 0) {
            int c = num % 10;
            if(c != 0) {
                res.insert(0,numMap.get(c) + units[indexOfUnits]);
            }else {
                if(res.length() != 0 && !res.substring(0,1).equals("零")) {
                    res.insert(0,"零");
                }
            }
            indexOfUnits += 1;
            num /= 10;
        }
        return res.toString();
    }

    public static void main(String[] args) {
        int numOfSheep = 99999;
        CountingSheep countingSheep = new CountingSheep();
        for (int i=1; i<=numOfSheep; i++) {
            System.out.println(countingSheep.readAs(i)+"只羊");
        }
    }
}