Java - Set collection interfaces

Set collection interface:

A Set is a Collection that cannot contain duplicate elements. The Java platform contains three general-purpose Set implementations: HashSet, TreeSet, and LinkedHashSet
HashSet: This class implements the Set interface, backed by a hash table (actually a HashMap instance). It makes no guarantees as to the iteration order of the set; in particular, it does not
guarantee that the order will remain constant over time. This class permits the null element.

   HashSet<String> hs =new HashSet<String>();
   hs.add("Name 1");
   hs.add("Name 2");
   hs.add("Name 3");

      int sizehashset = hs.size();
      System.out.println(sizehashset);
      Iterator<String> itr=hs.iterator();

    while(itr.hasNext()){
         System.out.println(itr.next()); }

   hs.contains(Object) ;

   hs.clear();

TreeSet : TreeSet provides an implementation of the Set interface that uses a tree for storage. Objects are stored in sorted, ascending order. The TreeSet class implements NavigableSet interface that extends the SortedSet interface. Access and retrieval times are quite fast.

LinkedHashSet :  LinkedHashSet is between HashSet and TreeSet. It is implemented as a hash table with a linked list running through it, so it provides the order of insertion.

LinkedHashSet maintains a linked list of the entries in the set, in the order in which they were inserted. This allows insertion-order iteration over the set.