A question on Interfaces.

[fatabass]

This is from the book SAMS Java in 21 Days:

Remember that almost everywhere that you can use a class, you can use an interface
instead. For example, you can declare a variable to be of an interface type:
Iterator loop = new Iterator()
When a variable is declared to be of an interface type, it simply means that the object is
expected to have implemented that interface. In this case, because Iterator contains an
object of the type Iterator, the assumption is that you can call all three of the interface’s
methods on that object: hasNext(), next(), and remove().

Especially this:

Remember that almost everywhere that you can use a class, you can use an interface
instead.

What does that mean ?

[Norm]

If its is referring to an object's datatype, then there is no difference between a class that extends a class or a class that implements an interface. Both techniques will give the class a datatype.
When a method requires an object of a specific datatype, like when adding a listener, that datatype can be given to the object in the two ways.

[fatabass]

When a method requires an object of a specific datatype, like when adding a listener, that datatype can be given to the object in the two ways.

So if a method requires a type of Interface f, and if my class MyClass is implementing f, that method can get a reference of type MyClass. Is this all that text is saying ?

[Norm]

What you say seems correct. I don't know what the author of the text meant.

[fatabass]

Thanks.