# Class IndexedTreeSet<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractSet<E>
com.macrofocus.utils.IndexedTreeSet<E>

Type Parameters:
  `E` - the type of elements maintained by this set

All Implemented Interfaces:
  `IndexedNavigableSet<E>, Serializable, Cloneable, Iterable<E>, Collection<E>, NavigableSet<E>, SequencedCollection<E>, SequencedSet<E>, Set<E>, SortedSet<E>`

public class IndexedTreeSet<E> extends AbstractSet<E> implements IndexedNavigableSet<E>, Cloneable, Serializable
A `NavigableSet` implementation based on a `IndexedTreeMap`. The elements are ordered using their natural ordering, or by a `Comparator` provided at set creation time, depending on which constructor is used.

This implementation provides guaranteed log(n) time cost for the basic operations (`add`, `remove` and `contains`).

Note that the ordering maintained by a set (whether or not an explicit comparator is provided) must be consistent with equals if it is to correctly implement the `Set` interface. (See `Comparable` or `Comparator` for a precise definition of consistent with equals.) This is so because the `Set` interface is defined in terms of the `equals` operation, but a `IndexedTreeSet` instance performs all element comparisons using its `compareTo` (or `compare`) method, so two elements that are deemed equal by this method are, from the standpoint of the set, equal. The behavior of a set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the `Set` interface.

Note that this implementation is not synchronized. If multiple threads access a tree set concurrently, and at least one of the threads modifies the set, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the set. If no such object exists, the set should be "wrapped" using the `Collections.synchronizedSortedSet` method. This is best done at creation time, to prevent accidental unsynchronized access to the set:

      SortedSet s = Collections.synchronizedSortedSet(new IndexedTreeSet(...));

The iterators returned by this class's `iterator` method are fail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's own `remove` method, the iterator will throw a `ConcurrentModificationException`. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw `ConcurrentModificationException` on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

This class is a member of the Java Collections Framework.

Since:
  1.2
See Also:
  - `Collection`
  - `Set`
  - `HashSet`
  - `Comparable`
  - `Comparator`
  - `IndexedTreeMap`
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `IndexedTreeSet()`
  Constructs a new, empty tree set, sorted according to the natural ordering of its elements.
  `IndexedTreeSet(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.
  `IndexedTreeSet(Comparator<? super E> comparator)`
  Constructs a new, empty tree set, sorted according to the specified comparator.
  `IndexedTreeSet(SortedSet<E> s)`
  Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `add(E e)`
  Adds the specified element to this set if it is not already present.
  `boolean`
  `addAll(Collection<? extends E> c)`
  Adds all of the elements in the specified collection to this set.
  `E`
  `ceiling(E e)`
  `void`
  `clear()`
  Removes all of the elements from this set.
  `Comparator<? super E>`
  `comparator()`
  `boolean`
  `contains(Object o)`
  Returns `true` if this set contains the specified element.
  `void`
  `debug()`
  `Iterator<E>`
  `descendingIterator()`
  Returns an iterator over the elements in this set in descending order.
  `NavigableSet<E>`
  `descendingSet()`
  `int`
  `entryIndex(E e)`
  Searches the specified tree map for the specified entry using the put algorithm.
  `E`
  `exact(int index)`
  Returns the entry located at the index offset from the beginning of the sorted set
  `E`
  `first()`
  `E`
  `floor(E e)`
  `SortedSet<E>`
  `headSet(E toElement)`
  `NavigableSet<E>`
  `headSet(E toElement, boolean inclusive)`
  `E`
  `higher(E e)`
  `boolean`
  `isEmpty()`
  Returns `true` if this set contains no elements.
  `Iterator<E>`
  `iterator()`
  Returns an iterator over the elements in this set in ascending order.
  `E`
  `last()`
  `E`
  `lower(E e)`
  `E`
  `pollFirst()`
  `E`
  `pollLast()`
  `boolean`
  `remove(Object o)`
  Removes the specified element from this set if it is present.
  `int`
  `size()`
  Returns the number of elements in this set (its cardinality).
  `NavigableSet<E>`
  `subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)`
  `SortedSet<E>`
  `subSet(E fromElement, E toElement)`
  `SortedSet<E>`
  `tailSet(E fromElement)`
  `NavigableSet<E>`
  `tailSet(E fromElement, boolean inclusive)`

  ### Methods inherited from class AbstractSet

  `equals, hashCode, removeAll`

  ### Methods inherited from class AbstractCollection

  `containsAll, retainAll, toArray, toArray, toString`

  ### Methods inherited from class Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

  ### Methods inherited from interface Collection

  `parallelStream, removeIf, stream, toArray`

  ### Methods inherited from interface Iterable

  `forEach`

  ### Methods inherited from interface NavigableSet

  `removeFirst, removeLast, reversed`

  ### Methods inherited from interface Set

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

  ### Methods inherited from interface SortedSet

  `addFirst, addLast, getFirst, getLast, spliterator`

- ## Constructor Details

  - ### IndexedTreeSet

    public IndexedTreeSet()
    Constructs a new, empty tree set, sorted according to the natural ordering of its elements. All elements inserted into the set must implement the `Comparable` interface. Furthermore, all such elements must be mutually comparable: `e1.compareTo(e2)` must not throw a `ClassCastException` for any elements `e1` and `e2` in the set. If the user attempts to add an element to the set that violates this constraint (for example, the user attempts to add a string element to a set whose elements are integers), the `add` call will throw a `ClassCastException`.

  - ### IndexedTreeSet

    public IndexedTreeSet(Comparator<? super E> comparator)
    Constructs a new, empty tree set, sorted according to the specified comparator. All elements inserted into the set must be mutually comparable by the specified comparator: `comparator.compare(e1, e2)` must not throw a `ClassCastException` for any elements `e1` and `e2` in the set. If the user attempts to add an element to the set that violates this constraint, the `add` call will throw a `ClassCastException`.
    Parameters:
      `comparator` - the comparator that will be used to order this set. If `null`, the natural ordering of the elements will be used.

  - ### IndexedTreeSet

    public IndexedTreeSet(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. All elements inserted into the set must implement the `Comparable` interface. Furthermore, all such elements must be mutually comparable: `e1.compareTo(e2)` must not throw a `ClassCastException` for any elements `e1` and `e2` in the set.
    Parameters:
      `c` - collection whose elements will comprise the new set
    Throws:
      `ClassCastException` - if the elements in `c` are not `Comparable`, or are not mutually comparable
      `NullPointerException` - if the specified collection is null

  - ### IndexedTreeSet

    public IndexedTreeSet(SortedSet<E> s)
    Constructs a new tree set containing the same elements and using the same ordering as the specified sorted set.
    Parameters:
      `s` - sorted set whose elements will comprise the new set
    Throws:
      `NullPointerException` - if the specified sorted set is null

- ## Method Details

  - ### iterator

    public Iterator<E> iterator()
    Returns an iterator over the elements in this set in ascending order.
    Specified by:
      `iterator` in interface `Collection<E>`
    Specified by:
      `iterator` in interface `Iterable<E>`
    Specified by:
      `iterator` in interface `NavigableSet<E>`
    Specified by:
      `iterator` in interface `Set<E>`
    Specified by:
      `iterator` in class `AbstractCollection<E>`
    Returns:
      an iterator over the elements in this set in ascending order

  - ### descendingIterator

    public Iterator<E> descendingIterator()
    Returns an iterator over the elements in this set in descending order.
    Specified by:
      `descendingIterator` in interface `NavigableSet<E>`
    Returns:
      an iterator over the elements in this set in descending order
    Since:
      1.6

  - ### descendingSet

    public NavigableSet<E> descendingSet()
    Specified by:
      `descendingSet` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### size

    public int size()
    Returns the number of elements in this set (its cardinality).
    Specified by:
      `size` in interface `Collection<E>`
    Specified by:
      `size` in interface `Set<E>`
    Specified by:
      `size` in class `AbstractCollection<E>`
    Returns:
      the number of elements in this set (its cardinality)

  - ### isEmpty

    public boolean isEmpty()
    Returns `true` if this set contains no elements.
    Specified by:
      `isEmpty` in interface `Collection<E>`
    Specified by:
      `isEmpty` in interface `Set<E>`
    Overrides:
      `isEmpty` in class `AbstractCollection<E>`
    Returns:
      `true` if this set contains no elements

  - ### contains

    public boolean contains(Object o)
    Returns `true` if this set contains the specified element. More formally, returns `true` if and only if this set contains an element `e` such that `(o==null ? e==null : o.equals(e))`.
    Specified by:
      `contains` in interface `Collection<E>`
    Specified by:
      `contains` in interface `Set<E>`
    Overrides:
      `contains` in class `AbstractCollection<E>`
    Parameters:
      `o` - object to be checked for containment in this set
    Returns:
      `true` if this set contains the specified element
    Throws:
      `ClassCastException` - if the specified object cannot be compared with the elements currently in the set
      `NullPointerException` - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements

  - ### add

    public boolean add(E e)
    Adds the specified element to this set if it is not already present. More formally, adds the specified element `e` to this set if the set contains no element `e2` such that `(e==null ? e2==null : e.equals(e2))`. If this set already contains the element, the call leaves the set unchanged and returns `false`.
    Specified by:
      `add` in interface `Collection<E>`
    Specified by:
      `add` in interface `Set<E>`
    Overrides:
      `add` in class `AbstractCollection<E>`
    Parameters:
      `e` - element to be added to this set
    Returns:
      `true` if this set did not already contain the specified element
    Throws:
      `ClassCastException` - if the specified object cannot be compared with the elements currently in this set
      `NullPointerException` - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements

  - ### remove

    public boolean remove(Object o)
    Removes the specified element from this set if it is present. More formally, removes an element `e` such that `(o==null ? e==null : o.equals(e))`, if this set contains such an element. Returns `true` if this set contained the element (or equivalently, if this set changed as a result of the call). (This set will not contain the element once the call returns.)
    Specified by:
      `remove` in interface `Collection<E>`
    Specified by:
      `remove` in interface `Set<E>`
    Overrides:
      `remove` in class `AbstractCollection<E>`
    Parameters:
      `o` - object to be removed from this set, if present
    Returns:
      `true` if this set con tained the specified element
    Throws:
      `ClassCastException` - if the specified object cannot be compared with the elements currently in this set
      `NullPointerException` - if the specified element is null and this set uses natural ordering, or its comparator does not permit null elements

  - ### clear

    public void clear()
    Removes all of the elements from this set. The set will be empty after this call returns.
    Specified by:
      `clear` in interface `Collection<E>`
    Specified by:
      `clear` in interface `Set<E>`
    Overrides:
      `clear` in class `AbstractCollection<E>`

  - ### addAll

    public boolean addAll(Collection<? extends E> c)
    Adds all of the elements in the specified collection to this set.
    Specified by:
      `addAll` in interface `Collection<E>`
    Specified by:
      `addAll` in interface `Set<E>`
    Overrides:
      `addAll` in class `AbstractCollection<E>`
    Parameters:
      `c` - collection containing elements to be added to this set
    Returns:
      `true` if this set changed as a result of the call
    Throws:
      `ClassCastException` - if the elements provided cannot be compared with the elements currently in the set
      `NullPointerException` - if the specified collection is null or if any element is null and this set uses natural ordering, or its comparator does not permit null elements

  - ### subSet

    public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
    Specified by:
      `subSet` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### headSet

    public NavigableSet<E> headSet(E toElement, boolean inclusive)
    Specified by:
      `headSet` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### tailSet

    public NavigableSet<E> tailSet(E fromElement, boolean inclusive)
    Specified by:
      `tailSet` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### subSet

    public SortedSet<E> subSet(E fromElement, E toElement)
    Specified by:
      `subSet` in interface `NavigableSet<E>`
    Specified by:
      `subSet` in interface `SortedSet<E>`

  - ### headSet

    public SortedSet<E> headSet(E toElement)
    Specified by:
      `headSet` in interface `NavigableSet<E>`
    Specified by:
      `headSet` in interface `SortedSet<E>`

  - ### tailSet

    public SortedSet<E> tailSet(E fromElement)
    Specified by:
      `tailSet` in interface `NavigableSet<E>`
    Specified by:
      `tailSet` in interface `SortedSet<E>`

  - ### comparator

    public Comparator<? super E> comparator()
    Specified by:
      `comparator` in interface `SortedSet<E>`

  - ### first

    public E first()
    Specified by:
      `first` in interface `SortedSet<E>`

  - ### last

    public E last()
    Specified by:
      `last` in interface `SortedSet<E>`

  - ### lower

    public E lower(E e)
    Specified by:
      `lower` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### floor

    public E floor(E e)
    Specified by:
      `floor` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### ceiling

    public E ceiling(E e)
    Specified by:
      `ceiling` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### higher

    public E higher(E e)
    Specified by:
      `higher` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### pollFirst

    public E pollFirst()
    Specified by:
      `pollFirst` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### pollLast

    public E pollLast()
    Specified by:
      `pollLast` in interface `NavigableSet<E>`
    Since:
      1.6

  - ### exact

    public E exact(int index)
    Description copied from interface: `IndexedNavigableSet`
    Returns the entry located at the index offset from the beginning of the sorted set
    Specified by:
      `exact` in interface `IndexedNavigableSet<E>`
    Parameters:
      `index` - index of the entry
    Returns:
      the entry located at the index (@code index) offset from the beginning of the sorted set

  - ### entryIndex

    public int entryIndex(E e)
    Description copied from interface: `IndexedNavigableSet`
    Searches the specified tree map for the specified entry using the put algorithm. Calculates its offset from the beginning of the sorted map using weights.
    Specified by:
      `entryIndex` in interface `IndexedNavigableSet<E>`
    Parameters:
      `e` - the entry
    Returns:
      index of the searched entry, if it is contained in the tree map; otherwise a NullPointerException is thrown

  - ### debug

    public void debug() throws Exception
    Throws:
      `Exception`