Re: Generics syntax and Comparing Comparables of type ?

From:

Hendrik Maryns <hendrik_maryns@despammed.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 12 Jul 2007 17:32:48 +0200

Message-ID:

<f75hc9$hlq$1@newsserv.zdv.uni-tuebingen.de>

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Piotr Kobzda schreef:

Hendrik Maryns wrote:

You will have to make RangedKey a
top-level class for this to work.

Not necessarily. Having it nested, you can import it, or use its
qualified name (RangedMap.RangedKey).

I do not really understand why.

Because a class body defines a namespace separated from a header of a
class declaration (i.e. modifiers, name, type parameters, etc.).

Ah, thanks.

Indeed, the following works as well:

/**
* Date: Jul 9, 2007
* Time: 4:25:18 PM
* This Map allows for a ranged mapping of values. The key can be
anything comparable such
* as Numbers and Dates or Strings
*/

import java.util.TreeMap;
import java.util.Map;

public class RangedMap<T extends Comparable<T>, V> extends
TreeMap<RangedMap.RangedKey<T>, V> {

    public static void main(String[] args) {
        Map<RangedKey<Integer>, String> testMap = new RangedMap<Integer,
String>();
        testMap.put(new RangedKey<Integer>(50, 60), "Blue");
        testMap.put(new RangedKey<Integer>(61, 70), "Yellow");
        testMap.put(new RangedKey<Integer>(71, 80), "Red");

        System.out.println(testMap.get(new RangedKey<Integer>(55)));
        System.out.println(testMap.get(new RangedKey<Integer>(67)));
        System.out.println(testMap.get(new RangedKey<Integer>(73)));

        System.out.println(testMap.get(new RangedKey<Integer>(1)));
        System.out.println(testMap.get(new RangedKey<Integer>(90)));

        testMap.put(new RangedKey<Integer>(62, 80), "Fail");

    }

    @Override
    public V put(RangedKey<T> key, V value) {
        rangeCheck(key.getMin());
        rangeCheck(key.getMax());

        return super.put(key, value);
    }

    @Override
    public void putAll(Map<? extends RangedKey<T>, ? extends V> map) {
        for (Map.Entry<? extends RangedKey<T>, ? extends V> entry :
map.entrySet())
            put(entry.getKey(), entry.getValue());
    }

    private void rangeCheck(T c) throws IllegalArgumentException {
        V val = get(new RangedKey<T>(c));
        if (val != null)
            throw new IllegalArgumentException("range: " + c + "overlaps
with another range and would cause an ambiguous mapping");
    }

    /**
     * A key which represents a range.
     *
     * @param <T> The comparable class which has ranges.
     */
    public static final class RangedKey<T extends Comparable<T>> implements
            Comparable<RangedKey<T>> {

        private T min;

        private T max;

        public int compareTo(RangedKey<T> range) {

            if (this.max.compareTo(range.min) < 0)
                return -1;
            if (this.min.compareTo(range.max) > 0)
                return 1;
            else
                return 0;
        }

        public RangedKey(T single) {
            this.min = single;
            this.max = single;
        }

        public RangedKey(T min, T max) {
            this.min = min;
            this.max = max;
        }

        public T getMin() {
            return min;
        }

        public T getMax() {
            return max;
        }

        @Override
        public String toString() {
            return min + "-" + max;
        }
    }
}

H.
- --
Hendrik Maryns
http://tcl.sfs.uni-tuebingen.de/~hendrik/
==================
http://aouw.org
Ask smart questions, get good answers:
http://www.catb.org/~esr/faqs/smart-questions.html
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFGlkmge+7xMGD3itQRAv8aAJsHURJ2p+sl90LWRn/bdFPq5N3AaACfZhHw
ipnThRxo2PZRO1tA3Vt1RjY=
=l4d2
-----END PGP SIGNATURE-----