Re: Generics & Comparable
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Ron Albright schreef:
I'm confused. This may not even make sense but in trying to figure it out
I think I've fried my brain beyond rational thought.
Can you generisize a class C such that the compareTo will only work for
any 2 generic types T1 & T2 given a common comparable ancestor of T1 & T2?
Something like this (only this doesn't work):
With this C:
public class C<T extends Comparable<? super T>>
implements Comparable<C<? extends T>>
{
private T val;
public C(T val)
{
this.val = val;
}
public T getValue()
{
return val;
}
public int compareTo(C<? extends T> obj)
{
return getValue().compareTo(obj.getValue());
}
}
the following works:
import java.util.Date;
import java.sql.Timestamp;
public class Ctest
{
public final void testCompareTo()
{
C<Date> dt = new C<Date>(new Date());
C<Date> dt2 = new C<Date>(new Date());
C<Timestamp> ts = new C<Timestamp>(new Timestamp(3));
C<Date> tsAsDate = new C<Date>(new Timestamp(4));
dt.compareTo(ts);
dt.compareTo(dt2);
// ts.compareTo(dt);
tsAsDate.compareTo(dt);
}
}
Of course the commented out line does not work, since Date is not a
subclass of TimeStamp, but rather the inverse.
You might want to consider whether you really need to know whether
TimeStamps are TimeStamps, or rather just Dates...
H.
- --
Hendrik Maryns
http://tcl.sfs.uni-tuebingen.de/~hendrik/
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