Re: Table object

Tom Anderson <>
Sat, 18 Jul 2009 00:41:44 +0100
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On Fri, 17 Jul 2009, Philipp wrote:

On Jul 17, 11:37?am, Alessio Stalla <> wrote:

On Jul 17, 11:30?am, Philipp <> wrote:

I'm looking for a collection which behaves like a two column table
(ordered key - value pairs, key not unique). Is there such a thing
either in the JRE or Apache collections?

A list of tuples?

class Tuple<K, V> {
? K key;
? V value;


It's not exactly clear what you want: "ordered" pairs - ordered how?
By order of insertion, or by Comparable/Comparator?

key - value pairs: do you need collection.get(key) ==> value?
collection.indexOf(key)? etc.

You could have to subclass some java.util.*List class.

Yes sorry I forgot to mention that I would like to have it implement
Map. Thus have something like a Collection which at the same time
implement List and Map (which is not possible).

The behaviour you want can be got from a TreeMap (a map which effectively
keeps its keys in sorted order) which contains LinkedHashSets (sets which
keep their elements in insertion order). But not the interface. I would
suggest you write a wrapper of your own - not necessarily implementing
Map, since it's not really a Map - around those classes.

For situations where you want it to act like a Map or a List, you could
have methods:

public Map<K, V> firstValues();
public List<V> values();

Which act like Map.entrySet, returning a 'live' collection which is a view
on the data in the table. Don't ask me how you'll implement add() on the
List view, though.

The code you've already written is probably simpler, though!


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