Java Reference
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Listing2-43 retrofits Listing2-33 ' sclasshierarchytotakeadvantageof Listing2-42 ' s
Drawable interface. You will notice that each of classes Point and Circle im-
plementsthisinterfacebyattachingthe implements Drawable clausetoitsclass
method header, and a code body to go with the method header.
Caution When implementing a method, do not forget that the interface's methods
areimplicitlydeclared public .Ifyouforgettoinclude public intheimplemented
method's declaration, the compiler will report an error because you are attempting to
assign weaker access to the implemented method.
the @Override annotation). This is known as interface inheritance .
It turns out that Circle 's header does not need the implements Drawable
clause.Ifthisclauseisnotpresent, Circle inherits Point 's draw() method,andis
still considered to be a Drawable , whether or not it overrides this method.
An interface specifies a type whose data values are the objects whose classes im-
plement the interface, and whose behaviors are those specified by the interface. This
fact implies that you can assign an object's reference to a variable of the interface
type,providedthattheobject'sclassimplements theinterface. Thefollowingexample
provides a demonstration:
public static void main(String[] args)
Drawable[] drawables = new Drawable[] { new Point(10,
20, 30) };
for (int i = 0; i < drawables.length; i++)
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