The Java Language Specification, Third Edition

CLASSES Superinterfaces 8.1.5
results in a compile-time error because the names java.lang.Cloneable and
Cloneable refer to the same interface.
An interface type I is a superinterface of class type C if any of the following
is true:
• I is a direct superinterface of C.
• C has some direct superinterface J for which I is a superinterface, using the
definition of “superinterface of an interface” given in §9.1.3.
• I is a superinterface of the direct superclass of C.
A class is said to implement all its superinterfaces.
In the example:
public interface Colorable {
void setColor(int color);
int getColor();
}
public enum Finish {MATTE, GLOSSY}
public interface Paintable extends Colorable {
void setFinish(Finish finish);
Finish getFinish();
}
class Point { int x, y; }
class ColoredPoint extends Point implements Colorable {
int color;
public void setColor(int color) { this.color = color; }
public int getColor() { return color; }
}
class PaintedPoint extends ColoredPoint implements Paintable
{
Finish finish;
public void setFinish(Finish finish) {
this.finish = finish;
}
public Finish getFinish() { return finish; }
}
the relationships are as follows:
• The interface Paintable is a superinterface of class PaintedPoint.
• The interface Colorable is a superinterface of class ColoredPoint and of
class PaintedPoint.
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