Add new class to determine the Java version

src/main/java/ctbrec/Java.java

@@ -0,0 +1,28 @@
+package ctbrec;
+
+public class Java {
+
+    public static int version() {
+        String specVersion = System.getProperty("java.specification.version");
+        switch(specVersion) {
+        case "1.7":
+            return 7;
+        case "1.8":
+            return 8;
+        case "9":
+            return 9;
+        case "10":
+            return 10;
+        case "11":
+            return 11;
+        case "12":
+            return 12;
+        default:
+            return 0;
+        }
+    }
+
+    public static void main(String[] args) {
+        System.out.println(Java.version());
+    }
+}