将int读到0显示为0000

int读0000时显示为0，谢了下面一个转换的小程序：

public class num {

	public  String getNumber(int num)
	{
		String result = "";
		switch ((num+"").length()) {
		case 1:
			result = "000" + num;
			break;
		case 2:
			result = "00" + 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;
	}
}

ArrayList<String> list = new ArrayList<String>();
for (int i = 1; i <= 9999; i++) {
    if (String.valueOf(i).length()==1) {
        list.add("000"+i);
    }else if (String.valueOf(i).length()==2){
        list.add("00"+i);
    }else if (String.valueOf(i).length()==3){
        list.add("0"+i);
    }else{
        list.add(String.valueOf(i));
    }
     
}