> > Just for curiosity what is the purpose of you own calendar class ?
>
> from Calendar apidoc:
> Subclasses of Calendar interpret a Date according to the rules of a
> specific calendar system. The platform provides one concrete
> subclass of
> Calendar: GregorianCalendar. Future subclasses could represent the
> various types of lunar calendars in use in many parts of the world.
>
> ..so there are more calendars planned in JDK and also there is no
> guarantee, that there are no other custom subclasses yet.
>
> I think it's a general rule, to take into accout subclasses,
> everywhere
> applicable (~ not final classes), esp. in tools, libraries,
> frameworks...
Indeed it is - and instanceof covers this. I've just knocked together (and
appended) a test case to illustrate and prove this : both java.util.Calendar
and my DummyCalendar are *both* instances of Calendar. This also holds true
of interfaces : if a class A implements interface B, an instance of of class
A is an instance of class B. Moreover, is class C extends class A, an
instance of class C is also an instance of class B.
Hopefully the test case is clearer and more lucid than this explanation :
Cheers,
Charles.
public class TestThingy extends TestCase {
public void testInstanceOf() {
assertTrue(new GregorianCalendar() instanceof java.util.Calendar);
assertTrue(new DummyCalendar() instanceof java.util.Calendar);
assertTrue(new AnObject() instanceof AnInterface);
assertTrue(new ASubclass() instanceof AnInterface);
}
public class DummyCalendar extends Calendar {
public void add(int field, int amount) {
}
protected void computeFields() {
}
protected void computeTime() {
}
public int getGreatestMinimum(int field) {
return 0;
}
public int getLeastMaximum(int field) {
return 0;
}
public int getMaximum(int field) {
return 0;
}
public int getMinimum(int field) {
return 0;
}
public void roll(int field, boolean up) {
}
}
public interface AnInterface {}
public class AnObject implements AnInterface {}
public class ASubclass extends AnObject {}
}
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