The TreeSet Interface implements the Set Interface in java collection and store the elements in a tree like structure. The TreeSet Interface and does not support duplicate elements like List Interface. The TreeSet Interface creates a empty TreeSet when constructor TreeSet() is invoked. The TreeSet Interface allows operations like Add elements, search elements, add elements at specified position, add elements from specified collection ,remove elements, etc.
The TreeSet interface is faster than LinkedHashSet interface but slower in comparison to HashSet due to its tree like structure for traversing the elements
The HashSet Interface class Hierarchy is given below
java.lang.Object
-> java.util.AbstractCollection<E>
->-> java.util.AbstractSet<E>
->->-> Hattersheim java.util.TreeSet<E>
The implemented interfaces by TreeSet Interface
Banning Serializable, Cloneable, Iterable<E>, Collection<E>, NavigableSet<E>, Set<E>, SortedSet<E>
The TreeSet Interface provides the below given constructors
| TreeSet Constructor | TreeSet Constructor Description |
| TreeSet() | creates a new empty tree set |
| TreeSet(Collection <? extends e> c) | creates a new tree set containing the elements in the specified collection , sorted as elements ordering |
| TreeSet(Comparator <? super E> comparator) | creates a new tree set containing the elements , sorted as specified comparator |
| TreeSet(SortedSet <E> s) | creates a new tree set containing the same elements with same ordering as the specified sorted set |
Methods for TreeSet Interface
The TreeSet Interface provides the below given methods for implementation
| TreeSet Methods | TreeSet Method Description |
| add(E e) | add the specified element to the set |
| clear() | removes all elements from the set |
| clone() | returns a shallow copy of the TreeSet instance |
| addAll(Collection < ? extends E > c) | allows to insert all elements in a specified collection to the set |
| ceiling(E e) | returns the least element in the set which is greater or equal to the given element |
| comparator() | returns NULL if set uses natural ordering of elements , else returns the comparator used to order elements in the set |
| contains(object o) | returns true if specified element presents in the set |
| descendingIterator() | returns an iterator over the elements in the set in descending order |
| descendingSet() | returns reverse element order from the list |
| first() | returns 1st elements in the set |
| floor(E e) | returns the highest element in the set which is less than or equal to the given element, else NULL |
| headSet( E toElement) | returns partial set view for elements which are less than toElement |
| higher( E e) | returns the lowest element in the set which is less than or equal to the given element, else NULL |
| isEmpty() | returns true if no element present in the set |
| iterator() | returns iterator over the elements in the set |
| last() | returns last element present in the set |
| lower( E e) | returns the highest element in the set which is less than or equal to the given element, else NULL |
| pollFirst() | returns and removes the first lowest element, else null |
| pollLast() | returns and removes the first highest element, else null |
| remove(object o) | remove the specified element if present in the set |
| size | returns Tree Set Size |
| spliterator() | Creates a late-binding and fail-fast Spliterator over the elements in the set |
| tailSet(E fromElement) | returns partial set view whose elements are greater than or equal to fromElement |
| tailSet(E fromElement boolean inclusive) | returns partial set view whose elements are greater than (or equal to, if inclusive is true) fromElement |
| subSet(E fromElement , E toElement) | returns partial set view whose elements range from fromElement, inclusive, to toElement, exclusive |
TreeSet Example in Java Collection
import java.util.*;
class FruitsTreeSet{
public static void main(String args[]){
//Create TreeSet object as fruits
TreeSet<String> fruits =new TreeSet<String>();
// Add elements to fruits
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");
fruits.add("Gauva");
fruits.add("Pears");
Iterator<String> itr =fruits.iterator();
while(itr.hasNext())
{
System.out.println(itr.next());
}
}
} 
