In addition, you learned how to implement interfaces and why multiple interface inheritance is safe ... and helped write a second Java book, Special Edition Using Java 2 Platform (QUE, 2001).

Abstract classes and interfaces in Java ... can implement more than one interface, but they can extend only one abstract class. This is a design decision based on the fact that multiple ...

Java's open inheritance model can ... classes is that they are declared using the sealed keyword, followed by the permits clause to explicitly name the classes that can extend or implement the sealed ...