Update solutions

Author: Sven97

src/Chapter05/Exercise0547_Business_check_ISBN_13.java

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+/**
+ * (Business: check ISBN-13) ISBN-13 is a new standard for identifying books. It uses
+ * 13 digits d1d2d3d4d5d6d7d8d9d10d11d12d13. The last digit d13 is a checksum, which is
+ * calculated from the other digits using the following formula:
+ * 10 - (d1 + 3d2 + d3 + 3d4 + d5 + 3d6 + d7 + 3d8 + d9 + 3d10 + d11 + 3d12),10
+ * If the checksum is 10, replace it with 0. Your program should read the input as a
+ * string. Here are sample runs:
+ *
+ * Enter the first 12 digits of an ISBN-13 as a string: 978013213080
+ * The ISBN-13 number is 9780132130806
+ * Enter the first 12 digits of an ISBN-13 as a string: 978013213079
+ * The ISBN-13 number is 9780132130790
+ * Enter the first 12 digits of an ISBN-13 as a string: 97801320
+ * 97801320 is an invalid input
+ *
+ * Created by Sven on 06/09/19.
+ */
+package Chapter05;
+
+import java.util.Scanner;
+
+public class Exercise0547_Business_check_ISBN_13 {
+    public static void main(String[] args) {
+        Scanner input = new Scanner(System.in);
+        System.out.print("Enter the first 12 digits of an ISBN as integer: ");
+        String originalNum = input.next();
+
+        if (originalNum.length() != 12) {
+            System.out.println(originalNum + " is an invalid input");
+        } else {
+            int sum = 0;
+            for (int i = 0; i < originalNum.length(); i++) {
+                sum += (i % 2 == 0) ? 3 * (originalNum.charAt(i) - 48) : (originalNum.charAt(i) - 48);
+            }
+            int checksum = (10 - sum % 10) % 10; // If the checksum is 10, replace it with 0, therefore % 10
+
+            String ISBN13str = originalNum + checksum;
+
+            System.out.print("The ISBN-13 number is " + ISBN13str);
+        }
+    }
+}