how to get HashTable values as Arraylist?

Question

Hashtable hw

How can I convert its values to:

ArrayList <Word> arr

thanks.

• Andrei Fierbinteanu: I find this rather amusing :)
• Michael Mrozek: This always happens on easy questions. Personally I think it's classy to delete a duplicate answer you posted if it doesn't contribute anything more than an answer that was submitted before you, but people actually doing that is exceedingly rare
• jjnguy: @Michael, For me it is fun to race to be the first to answer, while still providing the best content.
• Michael Mrozek: @Justin Me too, but if you lose the race there's no point leaving your answer around unless it provides extra information the others don't. There are verbatim answers posted on this one -- that adds nothing of value
• jjnguy: @Michael I agree. But if I get an upvote or two, I'd like to keep that reputation around. I don't think it ads clutter (too much) if they are all correct.

Answer 1

Use the ArrayList constructor that takes a collection.

ArrayList<Word> arr = new ArrayList<Word>(hw.values());

Then every value that was in the HashTable will be in the new ArrayList.

You can find documentation about the constructor in the javadocs.

Answer 2

ArrayList<Word> arr = new ArrayList<Word>( hw.values() );

Answer 3

Also you can use

ArrayList<Word> arr = Collections.list(hw.keys());

for keys as ArrayList

• Aquarius Power: keys wanted thx! any idea why they return keys as enumeration and not collection?

Answer 4

use

hw.values();

it will simply return the Collection (like a List) of Word objects.

---

from javadocs

values

public Collection values()

Returns a Collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.