add some dockerfiles for testing against jdk9

docker/shared/src/main/java/HelloWorld.java

@@ -0,0 +1,13 @@
+@lombok.Data
+public class HelloWorld {
+    private final int answer;
+    
+    public static void main(String... args) {
+        System.out.println(new HelloWorld(42).getAnswer());
+    }
+    
+    @FunctionalInterface
+    interface Foo {
+        String name();
+    }
+}