So I’m in the process of sorting a HashMap by its values into a LinkedHashMap, and one of the intermediate steps is as follows:
List foo = new ArrayList(hm.values());
TreeSet bar = new TreeSet(foo);
Now, foo has a size of over 4000, but bar has a size of only 99. Is this some sort of memory allocation problem? What’s going on?
Any help would be greatly appreciated.
Does foo contain a lot of duplicates?
I can’t believe how obvious that is. As in, blindingly obvious. Maybe that’s why I missed it. 
Thank you.
I take it, then, that TreeSets can’t contain duplicates?
No problem.
And yes, sets in general cannot contain duplicates. I’m not intimately familiar with the Java libraries, so I’m not sure what class would suit you better.
If you’re looking for a tree map that can have multiple objects for one key, check out Google’s TreeMultimap at http://guava-libraries.googlecode.com/svn/trunk/javadoc/index.html . However, you can still only have one key-value pair (but you can store multiple values for the same key).