Why do we need interfaces in Java?

Question

In Java to implement multiple inheritance we use interfaces. Is it the only use of interfaces? If yes, what is the main use of interface in Java? Why do we need interfaces in Java?

Answer 1

I would say the main use is polymorphism, or the ability to perform the same operation on a number of different objects. If different objects all implement the same interface and have the same method, you can store all of those objects in a Vector, for example, and iterate through the Vector calling that method on each one.