The Security Manager API hasn't been an important Java security feature for many years. It was a security feature for Applets, and over the past decade it's bee

The Security Manager API hasn't been an important Java security feature for many years. It was a security feature for Applets, and over the past decade it's been used by a few applications mostly for monitoring/toy sandboxing. In any event, a vanishingly small number of applications use it. Strong encapsulation is part of a long-term effort to make Java more secure, as threats are changing. Also, encapsulation isn't a breaking change. Java's strong backward compatibility commitment is with respect to the Java SE specification. No APIs are affected. It's only internal classes that have always been subject to change, and with clear warnings that they must not be accessed, that are encapsulated.