/** * Calculate the check digit of HKID * - Zhang Haoran, 20070912 * */import java.util.Scanner;public class CheckDigit { // Define aliases for ASCII character code private static final int ASC_0=48, ASC_A=65; // Return the checkDigit produced from hkid // hkid is a string that looks like A123456 private static char check( String hkid ){ // Step 1: Map the leading alphabet to number: A=1, B=2, ... Z=26 // e.g. A is 65 in ASCII, so 65-65+1 gives 1 int s=((int)hkid.charAt(0)-ASC_A+1)*8; // Step 2: Add the other digits like A*8 + 1*7 + 2*6 + ... + 6*2 for(int i=1; i<7; i++){ s += ((int)hkid.charAt(i)-ASC_0) * (8-i); } // Step 3: s = 11 - (s mod 11) s = 11-s%11; // ans can be 1, 2, 3, ..., 10, 11. // Step 4: If s is 10, return A. If 11, return 0. Else return s. s = s%11; return (s==10)?'A':(char)(s+ASC_0); } // Main method begins execution of Java application public static void main( String [] args ) { System.out.print( "Enter the first 7 digits of your HKID (e.g. A123456): " ); Scanner input = new Scanner( System.in ); String hkid = input.nextLine(); // read in a whole line, assuming correct format System.out.printf( "Your ID number is %s(%c).\n", hkid, CheckDigit.check(hkid)); } //end method main} // end class ID