The following uses of ? fail to compile with javac:

error: incompatible types: <null> cannot be converted to MyValue1
      MyValue1? vBox = null;
                                    ^
error: '(' or '[' expected
      MyValue1?[] vBoxArray = new MyValue1?[42];
                                                                     ^
error: illegal start of expression
      MyValue1?[] vBoxArray = new MyValue1?[42];
                                                                        ^
error: incompatible types: bad type in conditional expression
        MyValue1? val = flag ? valueField1 : null;
                                                                 ^
error: incomparable types: MyValue1 and <null>
            if (box != null) {
                      ^


value class MyValue1 {
    final int x = 0;
}

public class Test {
    static final MyValue1 vField = new MyValue1();

    value class MyValue2 {
        final MyValue1? vBoxField;

        public MyValue2() {
            vBoxField = new MyValue1();
        }
    }

    public static void main(String[] args) { }
}

error: incompatible types: MyValue1 cannot be converted to Test.MyValue2
            vBoxField = new MyValue1();
                               ^


value class MyValue1 {
    final int x = 0;
    public int hash() { return 0; }
}

public class Test {

    value class MyValue2 {
        final MyValue1? vBoxField = null;
  
        public int test() {
            return vBoxField.hash();
        }
    }

    public static void main(String[] args) { }
}

error: cannot find symbol
            return vBoxField.hash();
                            ^


interface MyInterface {
    public void test(MyValue1? vt);
}

value class MyValue1 implements MyInterface {
    final int x = 0;

    @Override
    public void test(MyValue1? vt) { }
}

error: MyValue1 is not abstract and does not override abstract method test(MyValue1) in MyInterface
value class MyValue1 implements MyInterface {
      ^
Test.java:9: error: method does not override or implement a method from a supertype
    @Override
    ^