Re: Unchecked call to compareTo
Russell Wallace wrote:
Just plain old Objects. The idea is that there's data in rows and
columns, each column may contain BigDecimals, Strings, Dates or
whatever, and the intent is to sort records by the values in the
currently selected column. So in:
int compare(Record a, Record b) {
Comparable ca = (Comparable<?>) get(a);
Comparable cb = (Comparable<?>) get(b);
return ca.compareTo(cb);
}
ca represents record a's value in the currently selected column, ditto
cb for record b. ca and cb may be BigDecimal, String or whatever, but
they are guarenteed to be the same type (though I don't know how or if I
can tell the compiler that).
I think you need to restrict the columns to particular comparable type.
So you comparator ends up something like this:
class MyComparator<T extends Comparator<T>>
implements Comparator<Record>
{
private final Class<? extends T> clazz;
public MyComparator(Class<? extends T> clazz) {
if (clazz == null) {
throw new NullPointerException();
}
this.clazz = clazz;
}
public int compare(Record a, Record b) {
T ta = clazz.cast(get(a));
T tb = clazz.cast(get(b));
return ta.compareTo(tb);
}
...
}
(Disclaimer: I have not so much as attempted to compile that.)
Where's the catch? Well clazz cannot be a generic type (although T may
be). However, you are fine with BigDecimal, String, Date, etc.
Tom hawtin
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