Single Element Java Data Structures that overwrite

Question

I've been using TreeMap<String,Object> to store objects as they don't allow entries with duplicate keys,

Is there a a similar data structure that only takes in a value/key and doesn't allow duplicate entries?

so something like Type<String> where all the Strings have to be different (or they overwrite)

until now ive just been using Vector<String> with checks to see if an entry is already in the vector before adding it which is a bit messy.

Jiri Kremser · Accepted Answer · 2013-06-25T14:39:04.933

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Set is what you are looking for. There are couple of implementations of this interface. The most common is the HashSet (fast contains() operation but the order is not guaranteed), TreeSet (this is actually implementation of SortedSet, the instances stored in TreeSet should implement Comparable) and the last commonly used is the LinkedHashSet. The order of LinkedHashSet is derived from the time elements were added into the container.

Recently, I saw this handy diagram: diagram

edited Jun 25 '13 at 14:39

answered Jun 25 '13 at 14:27

Jiri Kremser

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I wish I had seen that before! – Eduardo Jun 25 '13 at 14:41
The image is good but lacks the explanation of `LinkedList` and `Deque` class implementations, but is good. – Luiggi Mendoza Jun 25 '13 at 14:44

score 5 · Answer 2 · edited May 23 '17 at 11:56

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You're looking for a Set<String>, more specifically a TreeSet<String>.

Also, please don't use Vector, instead use List backed by an ArrayList. Refer to:

edited May 23 '17 at 11:56

Community

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answered Jun 25 '13 at 14:27

Luiggi Mendoza

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score 3 · Answer 3 · answered Jun 25 '13 at 14:29

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You can use Set and the equivalent to what you propose is TreeSet. However I think HashSet will do better job for the task you describe.

answered Jun 25 '13 at 14:29

Ivaylo Strandjev

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Single Element Java Data Structures that overwrite

3 Answers3