Here are some other points:

• Only constants (i.e., variables that are static final) and methods can be listed in an interface.
• An interface can be derived from another interface or from several interfaces:

  0788: interface a extends b, c { ... }
  

• A class can implement more than one interface:

  0789: public class x implements y, z { ... }
  

• A class can be derived from another class as well as implement one or more interfaces:

  0790: public class x extends w implements y, z { ... }
  

We saw earlier that multiple inheritance is not possible in Java. An interface is Java's way of achieving some of the possibilities of multiple inheritance. It is an idea that is borrowed from the programming language Objective C.