JADE achieves this by the following mechanism.
Creates an interface, which defines a set of constant and method definitions. The defined interface methods act as a communication protocol for accessing implementing classes.
A class implements an interface, by agreeing to implement all of the interfaces methods. The implementing class is not required to belong to any predefined class hierarchy.
To implement an interface, a class makes an agreement to implement all of the methods defined by the interface (thereby establishing a communication protocol that can be used to interact with all implementing classes).