Remove duplicates

I read a nice post about removing duplicates from a list, I must say that im stunned that i didn’t think about it. It’s so dead simple.

I post here so I can find it the next time I might need such a little trick

public List removeDuplicates(List items) { Set set = new LinkedHashSet(); set.addAll(items); return new ArrayList(set); }

July 31, 2006 | Filed Under java

Comments

2 Responses to “Remove duplicates”

Brian on August 1st, 2006 12:51 am

You might be better off with the following….

public void removeDuplicates(List items) {
Set set = new LinkedHashSet();
set.addAll(items);
items.removeAll();
items.addAll(set);
}

This way you’ll still have the same object reference that you started with instead of a completely new list.
Stephen Colebourne on August 1st, 2006 4:05 am

Just be aware that this method does create a lot of objects behind the scenes. A LinkedHashSet uses a LinkedHashMap, which creates one entry (object) for every item added. Clearly these all need to be created and garbage collected. Depending on your setup that may be important. (Normally though, I would advise not worrying too much about object creation and gc But for a smaller list it may be quicker to deduplicate without the Set.

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