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× Java Utility Library


Java TreeSet Class

Java.util package provides a TreeSet class which is a NavigableSet implementation based on a TreeMap. The elements are ordered using their natural ordering, or by a Comparator provided at set creation time, depending on which constructor is used. The class guarantees that the Map will be in ascending key order and backed by a TreeMap.

Class declaration

The declaration of java.util.TreeSet class is:

public class TreeSet<E>
  extends AbstractSet<E>
    implements NavigableSet<E>, Cloneable, Serializable

Class Constructors

S.NConstructors & Description
1. TreeSet()
Constructs a new, empty tree set, sorted according to the natural ordering of its elements.
2. TreeSet(Collection<? extends E> c)
Constructs a new tree set containing the elements in the specified collection, sorted according to the natural ordering of its elements.
3. TreeSet(Comparator<? super E> comparator)
Constructs a new, empty tree set, sorted according to the specified comparator.
4. TreeSet(SortedSet<E> s)
Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.

java.util.TreeSet Methods

The java.util.TreeSet class has a number of methods which are listed below:

Member Methods

S.NMethods & Description
1. boolean add(E element)
Adds the specified element to this set if it is not already present.
2. boolean addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this set.
3. E ceiling(E e)
Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
4. void clear()
Removes all of the elements from this set.
5. Object clone()
Returns a shallow copy of this TreeSet instance.
6. Comparator<? super E> comparator()
Returns the comparator used to order the elements in this set, or null if this set uses the natural ordering of its elements.
7. boolean contains(Object o)
Returns true if this set contains the specified element.
8. Iterator<E> descendingIterator()
Returns an iterator over the elements in this set in descending order.
9. NavigableSet<E> descendingSet()
Returns a reverse order view of the elements contained in this set.
10. E first()
Returns the first (lowest) element currently in this set.
11. E floor(E e)
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
12. SortedSet<E> headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less than toElement.
13. NavigableSet<E> headSet(E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement.
14. E higher(E e)
Returns the least element in this set strictly greater than the given element, or null if there is no such element.
15. boolean isEmpty()
Returns true if this set contains no elements.
16. Iterator<E> iterator()
Returns an iterator over the elements in this set in ascending order.
17. E last()
Returns the last (highest) element currently in this set.
18. E lower(E e)
Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
19. E pollFirst()
Retrieves and removes the first (lowest) element, or returns null if this set is empty.
20. E pollLast()
Retrieves and removes the last (highest) element, or returns null if this set is empty.
21. boolean remove(Object obj)
Removes the specified element from this set if it is present.
22. int size()
Returns the number of elements in this set (its cardinality).
23. Spliterator<E> spliterator()
Creates a late-binding and fail-fast Spliterator over the elements in this set.
24. NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from fromElement to toElement.
25. SortedSet<E> subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
26. SortedSet<E> tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
27. NavigableSet<E> tailSet(E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.

Methods inherited

This class inherits the methods of following class:

  • java.lang.Object
  • java.util.AbstractCollection<E>
  • java.util.AbstractSet<E>

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