[JEP 416](https://openjdk.java.net/jeps/416) reimplements core reflection with method handles.   Code that depends upon highly implementation-specific and undocumented aspects of the existing implementation might be impacted. Issues that might arise include:
   - Code that inspects the internal generated reflection classes (such as, subclasses of `MagicAccessorImpl`) no longer works and must be updated.
   - Code that attempts to break the encapsulation and change the value of the private final `modifiers` field of `Method`, `Field` and `Constructor` class to be different from the underlying member might cause a runtime error. Such code must be updated.

To mitigate this compatibility risk, you can enable the old implementation as a workaround by using  `-Djdk.reflect.useDirectMethodHandle=false`.   We will remove the old core reflection implementation in a future release. The `-Djdk.reflect.useDirectMethodHandle=false` workaround will stop working at that point.