BillUtils.java

package fi.insomnia.bortal.utilities;

public class BillUtils {

	private static final int[] multipliers = new int[] { 7, 3, 1 };

	/**
	 * Calculates and return the reference number calculated from the given base
	 * @param base
	 * @return 
	 */
	public static Integer createReferenceNumber(Integer base) {
		return base * 10 + calculateChecksum(base);
		
	}
	/**
	 * This function will calculate the checksum for the bills checksum 
	 * nuber for the given checksum base
	 * @param base The base of the checksum
	 * @return checksum integer in the range of 0-9 calculated from the given base 
	 */
	public static Integer calculateChecksum(Integer base)
	{
		int checksum = 0;
		for (int i = 0; base > 0; i++) {
			int num = base % 10;
			checksum += multipliers[i % multipliers.length] * num;
			base = base / 10;
		}

		return (checksum % 10 == 0 ? 0 : 10 - (checksum % 10));

	}

}