Answer: a function or procedure call from one object to another object
Explanation: UML(Unified Modeling language) behavioral modeling is the depiction of the relation of the elements in a dynamic manner and the dependency on time .Message in the UML behavioral modeling is a functional call taking place from one element to another.
The interaction is the model is seen through the flow of messages.Other options are incorrect because message is not information holding data structure, does not display the relation between object rather presents the flow and is not a memory location .
Answer:
Interfaces are way to use full abstraction.That;s why it is preffered over implementations.
Interfaces are just like class.But the methods declared inside an abstract class are by default abstract and the variables are by default static,final.Which is not the case with classes in classes the variables can be static or non- static ,fincal or non-final and methods can be abstract or non-abstract.
Java classes does not support multiple inheritance but interfaces support multiple inheritance.So whenever we want to implement multiple inheritance in Java we use interfaces.