Re: Encapsulating HashMap bulding
In article <qf1hu5d02ptja2duic3saa60qgolal9llm@4ax.com>,
Roedy Green <see_website@mindprod.com.invalid> wrote:
Can anyone think of a way to write a method that takes an array of X,
and produces a HashMap<Key,X>
How would you specify the name of the key field/method?
Maybe you could do it by making X implement an interface that defines
the key.
Perhaps you could do it with reflection.
If the key is easily derived from the value, what you might have is a
set rather than a map. If that's not the case, Generics trickery will
make it a simple task.
interface Key
{
boolean equals(Object other);
int hashCode ();
// Other stuff
}
interface Keyed
{
Key getKey();
}
public <K extends Keyed> HashMap <Key, K> keyedMap (K[] in)
{
HashMap<Key, K> map= new HashMap<Key, K>(in.length);
for (K keyed : in)
map.put(keyed.getKey(), keyed);
return map;
}
You could even put generics on they Key to support different categories
of keys. It would be nearing the boundary of where Generics stops
making coding easier, though.
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