Re: Unchecked call to compareTo

From:

Lew <lew@nowhere.com>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 02 Jan 2007 15:00:21 -0500

Message-ID:

<RIGdnW2_Ls9LJAfYnZ2dnUVZ_rGinZ2d@comcast.com>

Daniel Pitts wrote:

Russell Wallace wrote:

I'm trying to sort some data returned from a database (in rows and
columns, where a column may be BigDecimal, String or whatever, something
that implements compareTo anyway), and I'm fine up until the actual
comparison function. This is as close as I've got with it:

    int compare(Record a, Record b) {
        Comparable ca = (Comparable<?>) get(a);
        Comparable cb = (Comparable<?>) get(b);
        return ca.compareTo(cb);
    }

Please do not embed TAB characters in your posts.

I do not believe that suppressing the warning here is the answer, but instead
to declare the method with generic types in the first place.

Something along the lines of

<T extends Comparable<? super T>> int compare( T a, T b )
{
return a.compareTo( b );
}

The exact form depends on what you actually are trying to do: compare Records?
Compare a type buried in a Record? Compare the exact type, or things that
extend a common supertype?

You cannot cast with a generic because of type erasure, but here you likely do
not need such a cast.

Warning: I am still rough with generics, and I have not tried the code I
suggested.

- Lew