Re: Encapsulating HashMap bulding
On 11.05.2010 00:20, Roedy Green 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.
I'd rather provide an interface that is responsible for the conversion
from X to Key - this is more modular.
package util;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class MapUtil {
public interface Transformer<A, B> {
B transform(A a);
}
public static <K, V> Map<K, V> createHash(V[] i, Transformer<V, K> t) {
return createHash(Arrays.asList(i), t);
}
public static <K, V> Map<K, V> createHash(Iterable<V> i,
Transformer<V, K> t) {
final Map<K, V> map = new HashMap<K, V>();
fill(map, i, t);
return map;
}
public static <K, V> void fill(Map<K, V> m, Iterable<V> i,
Transformer<V, K> t) {
for (V val : i) {
m.put(t.transform(val), val);
}
}
}
Kind regards
robert
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