Re: LinkedHashMap next method ?
On Mon, 18 May 2009, Albert wrote:
Hi, since LinkedHashMap keep the insertion order, why sun didn't add the next
method: K next(K key) ?
Probably because they (and by 'they' i mean Josh Bloch, who wrote it)
didn't think of it, or didn't think it was important enough to include.
There are lots of potentially useful methods that classes in the standard
library could have but don't; that;s inevitable, and not an entirely bad
thing, as the alternative is classes with million of methods.
I need it because of speed of direct hash lookups (the hash part) and
order-based lookups (the next method). Is there an easy way to get that?
Copy:
https://openjdk.dev.java.net/source/browse/*checkout*/openjdk/jdk/trunk/jdk/src/share/classes/java/util/LinkedHashMap.java?rev=257
Paste. Edit:
package albert.util;
import java.util.*;
public K nextKey(K key) {
Entry<K, V> entry = (Entry<K, V>)getEntry(key);
if (entry == null) return null;
Entry<K, V> next = entry.after;
e.recordAccess(this);
if (next == null) return null;
return next.key;
}
Save. Profit!
Bear in mind that OpenJDK code is GPL'd, so if you want to redistribute
this class, you'l need to ship the source with it (and package it in a
separate package and JAR from the rest of your app to prevent GPL
infection).
tom
--
I am become Life, destroyer of worlds