Menu
Saw the code snippet like
Set<Record> instances = new HashSet<Record>(); I am wondering if Hashset is a special kind of set. Any difference between them?
849
A Set is a generic set of values with no duplicate elements. A TreeSet is a set where the elements are sorted. A HashSet is a set where the elements are not sorted or ordered.
Hash set and tree set both belong to the collection framework. HashSet is the implementation of the Set interface whereas Tree set implements sorted set. Tree set is backed by TreeMap while HashSet is backed by a hashmap. Sr.
Simply put, HashSet is faster than the TreeSet. HashSet provides constant-time performance for most operations like add(), remove() and contains(), versus the log(n) time offered by the TreeSet.
A Set represents a generic "set of values". A TreeSet is a set where the elements are sorted (and thus ordered), a HashSet is a set where the elements are not sorted or ordered.
A HashSet is typically a lot faster than a TreeSet.
A TreeSet is typically implemented as a red-black tree (See http://en.wikipedia.org/wiki/Red-black_tree - I've not validated the actual implementation of sun/oracle's TreeSet), whereas a HashSet uses Object.hashCode() to create an index in an array. Access time for a red-black tree is O(log(n)) whereas access time for a HashSet ranges from constant-time to the worst case (every item has the same hashCode) where you can have a linear search time O(n).
142
The HashSet is an implementation of a Set.
33
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
