Data commit

Task/Validate-International-Securities-Identification-Number/Java/validate-international-securities-identification-number.java

@@ -0,0 +1,47 @@
+public class ISIN {
+
+    public static void main(String[] args) {
+        String[] isins = {
+            "US0378331005",
+            "US0373831005",
+            "U50378331005",
+            "US03378331005",
+            "AU0000XVGZA3",
+            "AU0000VXGZA3",
+            "FR0000988040"
+        };
+        for (String isin : isins)
+            System.out.printf("%s is %s\n", isin, ISINtest(isin) ? "valid" : "not valid");
+    }
+
+    static boolean ISINtest(String isin) {
+        isin = isin.trim().toUpperCase();
+
+        if (!isin.matches("^[A-Z]{2}[A-Z0-9]{9}\\d$"))
+            return false;
+
+        StringBuilder sb = new StringBuilder();
+        for (char c : isin.substring(0, 12).toCharArray())
+            sb.append(Character.digit(c, 36));
+
+        return luhnTest(sb.toString());
+    }
+
+    static boolean luhnTest(String number) {
+        int s1 = 0, s2 = 0;
+        String reverse = new StringBuffer(number).reverse().toString();
+        for (int i = 0; i < reverse.length(); i++){
+            int digit = Character.digit(reverse.charAt(i), 10);
+            //This is for odd digits, they are 1-indexed in the algorithm.
+            if (i % 2 == 0){
+                s1 += digit;
+            } else { // Add 2 * digit for 0-4, add 2 * digit - 9 for 5-9.
+                s2 += 2 * digit;
+                if(digit >= 5){
+                    s2 -= 9;
+                }
+            }
+        }
+        return (s1 + s2) % 10 == 0;
+    }
+}