Re: Generics syntax and Comparing Comparables of type ?

From:

Joshua Cranmer <Pidgeot18@verizon.net>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 11 Jul 2007 21:23:04 GMT

Message-ID:

<YSbli.13264$g44.8829@trnddc02>

On Wed, 11 Jul 2007 17:29:08 +0000, Sideswipe wrote:

I am trying to write a RangedMap and when I "genericify" it, it occurred
to me that I am not completely sure how I can Quite express the syntax.
Admittedly I am learning my generics, but the code is definitely correct
when I remove the generics (run main for a test).

Essentially, I want to be able to apply this Map to any Comparable
object such as Date, Integer, String, whatever. Clearly though, the
comparison must be between comparables of the Same Type.

So, Comparable<?> min and Comparable<?> max could both be Integers, but
1 can't be Integer and the other Date. Maybe the code will explain
better. Anyone have some input?

    public static final class RangedKey implements
Comparable<RangedKey> {
        private Comparable<?> min;
        private Comparable<?> max;

This seems suspicious hacking used to avoid rare types. The answer is to
generify RangedKey to RangedKey<T>. A sample of code:

public static final class RangedKey<T extends Comparable<T>> implements
Comparable<RangedKey<T>> {
    private T min;
    private T max;

....

    public int compareTo(RangedKey<T extends Comparable<T>> range) {
        if (this.max.compareTo(range.min) < 0) {
....