Add support for newer Java versions

common/src/main/java/ctbrec/Java.java

@@ -2,6 +2,8 @@ package ctbrec;
 
 public class Java {
 
+    private Java() {}
+
     public static int version() {
         String specVersion = System.getProperty("java.specification.version");
         switch(specVersion) {
@@ -9,22 +11,12 @@ public class Java {
             return 7;
         case "1.8":
             return 8;
-        case "9":
-            return 9;
-        case "10":
-            return 10;
-        case "11":
-            return 11;
-        case "12":
-            return 12;
-        case "13":
-            return 13;
-        case "14":
-            return 14;
-        case "15":
-            return 15;
         default:
-            return 0;
+            try {
+                return Integer.parseInt(specVersion);
+            } catch (NumberFormatException nfe) {
+                return 0;
+            }
         }
     }
 }