Class TreeSet<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractSet<E>
java.util.TreeSet<E>
All Implemented Interfaces:
Iterable<E>, Collection<E>, NavigableSet<E>, Set<E>, SortedSet<E>
public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>

TreeSet is an implementation of SortedSet. All optional operations (adding and removing) are supported. The elements can be any objects which are comparable to each other either using their natural order or a specified Comparator.

Since

1.2

  • Constructor Summary

    Constructors
    Constructor
    Description
    TreeSet()
    Constructs a new empty instance of TreeSet which uses natural ordering.
    TreeSet(Collection<? extends E> collection)
    Constructs a new instance of TreeSet which uses natural ordering and containing the unique elements in the specified collection.
    TreeSet(Comparator<? super E> comparator)
    Constructs a new empty instance of TreeSet which uses the specified comparator.
    TreeSet(SortedSet<E> set)
    Constructs a new instance of TreeSet containing the elements of the specified SortedSet and using the same Comparator.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(E object)
    Adds the specified object to this TreeSet.
    boolean
    addAll(Collection<? extends E> collection)
    Adds the objects in the specified collection to this TreeSet.
    E
    ceiling(E e)
    Answers the smallest element bigger than or equal to the specified one, or null if no such element.
    void
    clear()
    Removes all elements from this TreeSet, leaving it empty.
    Comparator<? super E>
    comparator()
    Returns the comparator used to compare elements in this TreeSet.
    boolean
    contains(Object object)
    Searches this TreeSet for the specified object.
    Iterator<E>
    descendingIterator()
    Answers a descending iterator of this set.
    NavigableSet<E>
    descendingSet()
    Answers a reverse order view of this set.
    E
    first()
    Answers the first element in this TreeSet.
    E
    floor(E e)
    Answers the biggest element less than or equal to the specified one, or null if no such element.
    SortedSet<E>
    headSet(E end)
    Answers a SortedSet of the specified portion of this TreeSet which contains elements less than the end element.
    NavigableSet<E>
    headSet(E end, boolean endInclusive)
    Answers a NavigableSet of the specified portion of this set which contains elements less than (or equal to, depends on endInclusive) the end element.
    E
    higher(E e)
    Answers the smallest element bigger than the specified one, or null if no such element.
    boolean
    isEmpty()
    Returns true if this TreeSet has no element, otherwise false.
    Iterator<E>
    iterator()
    Returns an Iterator on the elements of this TreeSet.
    E
    last()
    Answers the last element in this TreeSet.
    E
    lower(E e)
    Answers the biggest element less than the specified one, or null if no such element.
    E
    pollFirst()
    Deletes and answers the smallest element, or null if the set is empty.
    E
    pollLast()
    Deletes and answers the biggest element, or null if the set is empty.
    boolean
    remove(Object object)
    Removes an occurrence of the specified object from this TreeSet.
    int
    size()
    Returns the number of elements in this TreeSet.
    NavigableSet<E>
    subSet(E start, boolean startInclusive, E end, boolean endInclusive)
    Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element but less than (or equal to, depends on endInclusive) the end element.
    SortedSet<E>
    subSet(E start, E end)
    Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element but less than the end element.
    SortedSet<E>
    tailSet(E start)
    Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element.
    NavigableSet<E>
    tailSet(E start, boolean startInclusive)
    Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element.

    Methods inherited from class AbstractSet

    equals, hashCode, removeAll

    Methods inherited from class AbstractCollection

    containsAll, retainAll, toArray, toArray, toString

    Methods inherited from class Object

    clone, getClass, notify, notifyAll, wait, wait, wait

    Methods inherited from interface Set

    containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray

  • Constructor Details

    • TreeSet

      public TreeSet()
      Constructs a new empty instance of TreeSet which uses natural ordering.

    • TreeSet

      public TreeSet(Collection<? extends E> collection)

      Constructs a new instance of TreeSet which uses natural ordering and containing the unique elements in the specified collection.

      Parameters
      • collection: the collection of elements to add.
      Throws
      • ClassCastException: @throws ClassCastException when an element in the collection does not implement the Comparable interface, or the elements in the collection cannot be compared.

    • TreeSet

      public TreeSet(Comparator<? super E> comparator)

      Constructs a new empty instance of TreeSet which uses the specified comparator.

      Parameters
      • comparator: the comparator to use.

    • TreeSet

      public TreeSet(SortedSet<E> set)

      Constructs a new instance of TreeSet containing the elements of the specified SortedSet and using the same Comparator.

      Parameters
      • set: the SortedSet of elements to add.

  • Method Details

    • add

      public boolean add(E object)

      Adds the specified object to this TreeSet.

      Parameters
      • object: the object to add.
      Returns
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface Set<E>
      Overrides:
      add in class AbstractCollection<E>
      Returns:

      true when this TreeSet did not already contain the object, false otherwise.

      Throws

      • ClassCastException: @throws ClassCastException when the object cannot be compared with the elements in this TreeSet.

      • NullPointerException: @throws NullPointerException when the object is null and the comparator cannot handle null.

    • addAll

      public boolean addAll(Collection<? extends E> collection)

      Adds the objects in the specified collection to this TreeSet.

      Parameters
      • collection: the collection of objects to add.
      Returns
      Specified by:
      addAll in interface Collection<E>
      Specified by:
      addAll in interface Set<E>
      Overrides:
      addAll in class AbstractCollection<E>
      Returns:

      true if this TreeSet was modified, false otherwise.

      Throws

      • ClassCastException: @throws ClassCastException when an object in the collection cannot be compared with the elements in this TreeSet.

      • NullPointerException: @throws NullPointerException when an object in the collection is null and the comparator cannot handle null.

    • clear

      public void clear()

      Removes all elements from this TreeSet, leaving it empty.

      See also

      • #isEmpty

      • #size

      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface Set<E>
      Overrides:
      clear in class AbstractCollection<E>

    • comparator

      public Comparator<? super E> comparator()

      Returns the comparator used to compare elements in this TreeSet.

      Returns

      a Comparator or null if the natural ordering is used

      Specified by:
      comparator in interface SortedSet<E>

    • contains

      public boolean contains(Object object)

      Searches this TreeSet for the specified object.

      Parameters
      • object: the object to search for.
      Returns
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface Set<E>
      Overrides:
      contains in class AbstractCollection<E>
      Returns:

      true if object is an element of this TreeSet, false otherwise.

      Throws

      • ClassCastException: @throws ClassCastException when the object cannot be compared with the elements in this TreeSet.

      • NullPointerException: @throws NullPointerException when the object is null and the comparator cannot handle null.

    • isEmpty

      public boolean isEmpty()

      Returns true if this TreeSet has no element, otherwise false.

      Returns

      true if this TreeSet has no element.

      See also
      • #size
      Specified by:
      isEmpty in interface Collection<E>
      Specified by:
      isEmpty in interface Set<E>
      Overrides:
      isEmpty in class AbstractCollection<E>
      Returns:

      true if this Collection has no elements, false otherwise.

      See also
      • #size

    • iterator

      public Iterator<E> iterator()

      Returns an Iterator on the elements of this TreeSet.

      Returns

      an Iterator on the elements of this TreeSet.

      See also
      • Iterator
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface Set<E>
      Specified by:
      iterator in class AbstractCollection<E>

    • descendingIterator

      public Iterator<E> descendingIterator()

      Answers a descending iterator of this set.

      Returns

      the descending iterator

      Since

      1.6

      See also
      • java.util.NavigableSet#descendingIterator()
      Specified by:
      descendingIterator in interface NavigableSet<E>

    • remove

      public boolean remove(Object object)

      Removes an occurrence of the specified object from this TreeSet.

      Parameters
      • object: the object to remove.
      Returns
      Specified by:
      remove in interface Collection<E>
      Specified by:
      remove in interface Set<E>
      Overrides:
      remove in class AbstractCollection<E>
      Returns:

      true if this TreeSet was modified, false otherwise.

      Throws

      • ClassCastException: @throws ClassCastException when the object cannot be compared with the elements in this TreeSet.

      • NullPointerException: @throws NullPointerException when the object is null and the comparator cannot handle null.

    • size

      public int size()

      Returns the number of elements in this TreeSet.

      Returns

      the number of elements in this TreeSet.

      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface Set<E>
      Specified by:
      size in class AbstractCollection<E>
      Returns:
      how many objects this Collection contains, or Integer.MAX_VALUE if there are more than Integer.MAX_VALUE elements in this Collection.

    • first

      public E first()

      Answers the first element in this TreeSet.

      Returns

      the first element

      Throws
      • NoSuchElementException: when this TreeSet is empty
      Specified by:
      first in interface SortedSet<E>

    • last

      public E last()

      Answers the last element in this TreeSet.

      Returns

      the last element

      Throws
      • NoSuchElementException: when this TreeSet is empty
      Specified by:
      last in interface SortedSet<E>

    • pollFirst

      public E pollFirst()

      Deletes and answers the smallest element, or null if the set is empty.

      Returns

      the smallest element, or null if the set is empty

      Since

      1.6

      See also
      • java.util.NavigableSet#pollFirst()
      Specified by:
      pollFirst in interface NavigableSet<E>

    • pollLast

      public E pollLast()

      Deletes and answers the biggest element, or null if the set is empty.

      Returns

      the biggest element, or null if the set is empty

      Since

      1.6

      See also
      • java.util.NavigableSet#pollLast()
      Specified by:
      pollLast in interface NavigableSet<E>

    • higher

      public E higher(E e)

      Answers the smallest element bigger than the specified one, or null if no such element.

      Parameters
      • e: the specified element
      Returns
      Since

      1.6

      See also
      • java.util.NavigableSet#higher(java.lang.Object)
      Specified by:
      higher in interface NavigableSet<E>
      Returns:

      the smallest element bigger than the specified one, or null if no such element

      Throws

      • ClassCastException: if the element cannot be compared with the ones in the set

      • NullPointerException: if the element is null and the set can not contain null

    • lower

      public E lower(E e)

      Answers the biggest element less than the specified one, or null if no such element.

      Parameters
      • e: the specified element
      Returns
      Since

      1.6

      See also
      • java.util.NavigableSet#lower(java.lang.Object)
      Specified by:
      lower in interface NavigableSet<E>
      Returns:

      the biggest element less than the specified one, or null if no such element

      Throws

      • ClassCastException: if the element cannot be compared with the ones in the set

      • NullPointerException: if the element is null and the set can not contain null

    • ceiling

      public E ceiling(E e)

      Answers the smallest element bigger than or equal to the specified one, or null if no such element.

      Parameters
      • e: the specified element
      Returns
      Since

      1.6

      See also
      • java.util.NavigableSet#ceiling(java.lang.Object)
      Specified by:
      ceiling in interface NavigableSet<E>
      Returns:

      the smallest element bigger than or equal to the specified one, or null if no such element

      Throws

      • ClassCastException: if the element cannot be compared with the ones in the set

      • NullPointerException: if the element is null and the set can not contain null

    • floor

      public E floor(E e)

      Answers the biggest element less than or equal to the specified one, or null if no such element.

      Parameters
      • e: the specified element
      Returns
      Since

      1.6

      See also
      • java.util.NavigableSet#floor(java.lang.Object)
      Specified by:
      floor in interface NavigableSet<E>
      Returns:

      the biggest element less than or equal to the specified one, or null if no such element

      Throws

      • ClassCastException: if the element cannot be compared with the ones in the set

      • NullPointerException: if the element is null and the set can not contain null

    • descendingSet

      public NavigableSet<E> descendingSet()

      Answers a reverse order view of this set.

      Returns

      the reverse order view

      Since

      1.6

      See also
      • java.util.NavigableSet#descendingSet()
      Specified by:
      descendingSet in interface NavigableSet<E>

    • subSet

      public NavigableSet<E> subSet(E start, boolean startInclusive, E end, boolean endInclusive)

      Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element but less than (or equal to, depends on endInclusive) the end element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

      Parameters

      • start: the start element

      • startInclusive: true if the start element is in the returned set

      • end: the end element

      • endInclusive: true if the end element is in the returned set

      Returns

      the subset

      Throws

      • ClassCastException: @throws ClassCastException when the start or end object cannot be compared with the elements in this set

      • NullPointerException: @throws NullPointerException when the start or end object is null and the set cannot contain null

      • IllegalArgumentException: @throws IllegalArgumentException when the start is bigger than end; or start or end is out of range and the set has a range

      Since

      1.6

      See also
      • java.util.NavigableSet#subSet(Object, boolean, Object, boolean)
      Specified by:
      subSet in interface NavigableSet<E>

    • headSet

      public NavigableSet<E> headSet(E end, boolean endInclusive)

      Answers a NavigableSet of the specified portion of this set which contains elements less than (or equal to, depends on endInclusive) the end element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

      Parameters

      • end: the end element

      • endInclusive: true if the end element is in the returned set

      Returns

      the subset

      Throws

      • ClassCastException: @throws ClassCastException when the end object cannot be compared with the elements in this set

      • NullPointerException: @throws NullPointerException when the end object is null and the set cannot contain handle null

      • IllegalArgumentException: when end is out of range and the set has a range

      Since

      1.6

      See also
      • java.util.NavigableSet#headSet(Object, boolean)
      Specified by:
      headSet in interface NavigableSet<E>

    • tailSet

      public NavigableSet<E> tailSet(E start, boolean startInclusive)

      Answers a NavigableSet of the specified portion of this set which contains elements greater (or equal to, depends on startInclusive) the start element. The returned NavigableSet is backed by this set so changes to one are reflected by the other.

      Parameters

      • start: the start element

      • startInclusive: true if the start element is in the returned set

      Returns

      the subset

      Throws

      • ClassCastException: @throws ClassCastException when the start object cannot be compared with the elements in this set

      • NullPointerException: when the start object is null and the set cannot contain null

      • IllegalArgumentException: when start is out of range and the set has a range

      Since

      1.6

      See also
      • java.util.NavigableSet#tailSet(Object, boolean)
      Specified by:
      tailSet in interface NavigableSet<E>

    • subSet

      public SortedSet<E> subSet(E start, E end)

      Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element but less than the end element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

      Parameters

      • start: the start element

      • end: the end element

      Returns
      Specified by:
      subSet in interface SortedSet<E>
      Returns:

      a subset where the elements are greater or equal to start and less than end

      Throws

      • ClassCastException: @exception ClassCastException when the start or end object cannot be compared with the elements in this TreeSet

      • NullPointerException: @exception NullPointerException when the start or end object is null and the comparator cannot handle null

    • headSet

      public SortedSet<E> headSet(E end)

      Answers a SortedSet of the specified portion of this TreeSet which contains elements less than the end element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

      Parameters
      • end: the end element
      Returns

      a subset where the elements are less than end

      Throws

      • ClassCastException: @exception ClassCastException when the end object cannot be compared with the elements in this TreeSet

      • NullPointerException: @exception NullPointerException when the end object is null and the comparator cannot handle null

      Specified by:
      headSet in interface SortedSet<E>

    • tailSet

      public SortedSet<E> tailSet(E start)

      Answers a SortedSet of the specified portion of this TreeSet which contains elements greater or equal to the start element. The returned SortedSet is backed by this TreeSet so changes to one are reflected by the other.

      Parameters
      • start: the start element
      Returns
      Specified by:
      tailSet in interface SortedSet<E>
      Returns:

      a subset where the elements are greater or equal to start

      Throws

      • ClassCastException: @exception ClassCastException when the start object cannot be compared with the elements in this TreeSet

      • NullPointerException: @exception NullPointerException when the start object is null and the comparator cannot handle null