Design Help/Suggestion required

I have an Application built 4 years back, The Application generates the 1,00,000 challans every year.

I am maintaining the separate table for storing the challans and I have the Challan Id(Auto Increment) and that I am using that as the Challan Number for the application.

Every since i am generating the challan Number, the length of the challans are increasing from 4 digit to 5digit and 5 digiti to 6 and continues... But I am getting the request to alter this and make it not go beyond 8 digit Challan Number.

Please suggest me any ideas which I can use it for to maintain the challan number by not exceeding the size of the number. I am using this challan Number t retrieve the payment recived and made by the people for the past period as well.

I have used the Java, Struts and MySql for this application

Pleas开发者_如何学JAVAe guide me with this design

If you are generating 100,000 challans a year, and you have an 8 digit space, then the math works out as

99,999,999 max challan number / 100,000 challans per year = 1,000 years of challans

Therefore, at your current rate, you will not fill up the table for the next 1,000 years.