How can I easily delete duplicates in a linked list in java?
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I left out some details, sorry, the data structure needed to be duplicate free, sorted, and able to have an iterator.Bobby– Bobby2009-05-29 16:22:22 +00:00Commented May 29, 2009 at 16:22
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1A SortedSet like TreeSet will do all this.Peter Lawrey– Peter Lawrey2009-06-01 20:58:49 +00:00Commented Jun 1, 2009 at 20:58
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@Peter Lawrey - Thanks, for the comment, I did discover the TreeSet data structure a couple days ago and it is exactly what I needed.Bobby– Bobby2009-06-02 03:29:22 +00:00Commented Jun 2, 2009 at 3:29
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6 Answers
Use a LinkedHashSet instead, and then you won't have duplicates in the first place.
3 Comments
Bill K
That's the exact answer :) I used to make those all the time before they existed in the API, LinkedHasSets rock.
Bill K
I keep looking at that typo thinking it should have a cat behind it. "Link can has sets?"
Jason S
+1 -- nice. consider adding a link to the appropriate Javadoc.
I don't know if your requirements is to use a linked list but if not, use a Set instead of a List (you tagged the question as 'best-practices')
1 Comment
Bobby
I ended up using a TreeSet instead of a plain set but it was your answer that got me to that conclusion, thanks again.
Easily in terms of what? If it's a reasonably short list, the simplest solution is to dump it to a Set and then back to a List.
myList = new LinkedList<Whatever>(new HashSet<Whatever>(myList));
But why bother with this? If you don't want duplicates, you should be using a Set; if you only want a list so that you can keep the elements in the same order they were inserted, you can use a LinkedHashSet to get the best of both worlds: a Set that iterates predictably like a LinkedList.
1 Comment
rodion
I agree with you not to use a List when a Set is needed. One minor detail to your code: myList = new LinkedList<Whatever>(new HashSet<Whatever>(myList)); (Since Set is an interface). Sorry for nitpicking ^^
Search through them and, if two represent the same thing, delete one of them.
What more do you want? Do you want advice on how to do this quickly? If that's the case, store the nodes in a hash table for easy matching when looking for duplicates.
Comments
import java.util.*;
import java.lang.*;
class Main
{
public static void main (String[] args) throws java.lang.Exception
{
Collection<String> c = new LinkedList<String>();
c.add("JAR");c.add("BDK");c.add("JDK");c.add("JAR");c.add("WAR");c.add("APK");c.add("BDK");
c=new HashSet(c);
c=new ArrayList(c);
for(String s : c)
{
System.out.println(s);
}
}
}
Comments
you can use the distinct() method of Stream. The distinct() method works based on Stream and returns a stream that contains only a unique element. This method internally invokes the equals() method.
duplicateElements.stream().distinct().collect(Collectors.toList());
