JEP-260 was implemented to make the Java platform more secure. The core of this JEP's goal was to encapsulate the majority of internal APIs. Specifically, most of the JDK's internal APIs are no longer accessible by default. Currently, internal APIs deemed to be critical and widely-used remain accessible. In the future, we are likely to see functionality to replace them, and at that time, those internal APIs will not be accessible by default.
So, why is this change necessary? There are a few widely-used APIs that are unstable and, in some cases, not standardized. Unsupported APIs should not have access to internal details of the JDK. Therefore, JEP-260 resulted in increased security of the Java platform. Generally speaking, you should not use unsupported APIs in your development projects.
The aforementioned critical APIs (internal to the...