E - the type of elements maintained by this setpublic interface NavigableSet<E> extends SortedSet<E>
SortedSet extended with navigation methods reporting
 closest matches for given search targets. Methods lower,
 floor, ceiling, and higher return elements
 respectively less than, less than or equal, greater than or equal,
 and greater than a given element, returning null if there
 is no such element.  A NavigableSet may be accessed and
 traversed in either ascending or descending order.  The descendingSet method returns a view of the set with the senses of
 all relational and directional methods inverted. The performance of
 ascending operations and views is likely to be faster than that of
 descending ones.  This interface additionally defines methods
 pollFirst and pollLast that return and remove the
 lowest and highest element, if one exists, else returning null.  Methods subSet, headSet,
 and tailSet differ from the like-named SortedSet methods in accepting additional arguments describing
 whether lower and upper bounds are inclusive versus exclusive.
 Subsets of any NavigableSet must implement the NavigableSet interface.
  The return values of navigation methods may be ambiguous in
 implementations that permit null elements. However, even
 in this case the result can be disambiguated by checking
 contains(null). To avoid such issues, implementations of
 this interface are encouraged to not permit insertion of
 null elements. (Note that sorted sets of Comparable elements intrinsically do not permit null.)
 
Methods
 subSet(E, E),
 headSet(E), and
 tailSet(E)
 are specified to return SortedSet to allow existing
 implementations of SortedSet to be compatibly retrofitted to
 implement NavigableSet, but extensions and implementations
 of this interface are encouraged to override these methods to return
 NavigableSet.
 
This interface is a member of the Java Collections Framework.
| Modifier and Type | Method and Description | 
|---|---|
| E | ceiling(E e)Returns the least element in this set greater than or equal to
 the given element, or  nullif there is no such element. | 
| Iterator<E> | descendingIterator()Returns an iterator over the elements in this set, in descending order. | 
| NavigableSet<E> | descendingSet()Returns a reverse order view of the elements contained in this set. | 
| E | floor(E e)Returns the greatest element in this set less than or equal to
 the given element, or  nullif there is no such element. | 
| SortedSet<E> | headSet(E toElement)Returns a view of the portion of this set whose elements are
 strictly less than toElement. | 
| 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  inclusiveis true)toElement. | 
| E | higher(E e)Returns the least element in this set strictly greater than the
 given element, or  nullif there is no such element. | 
| Iterator<E> | iterator()Returns an iterator over the elements in this set, in ascending order. | 
| E | lower(E e)Returns the greatest element in this set strictly less than the
 given element, or  nullif there is no such element. | 
| E | pollFirst()Retrieves and removes the first (lowest) element,
 or returns  nullif this set is empty. | 
| E | pollLast()Retrieves and removes the last (highest) element,
 or returns  nullif this set is empty. | 
| NavigableSet<E> | subSet(E fromElement,
      boolean fromInclusive,
      E toElement,
      boolean toInclusive)Returns a view of the portion of this set whose elements range from
  fromElementtotoElement. | 
| 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. | 
| SortedSet<E> | tailSet(E fromElement)Returns a view of the portion of this set whose elements are
 greater than or equal to fromElement. | 
| 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  inclusiveis true)fromElement. | 
comparator, first, last, spliteratoradd, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArrayparallelStream, removeIf, streamE lower(E e)
null if there is no such element.e - the value to matche,
         or null if there is no such elementClassCastException - if the specified element cannot be
         compared with the elements currently in the setNullPointerException - if the specified element is null
         and this set does not permit null elementsE floor(E e)
null if there is no such element.e - the value to matche,
         or null if there is no such elementClassCastException - if the specified element cannot be
         compared with the elements currently in the setNullPointerException - if the specified element is null
         and this set does not permit null elementsE ceiling(E e)
null if there is no such element.e - the value to matche,
         or null if there is no such elementClassCastException - if the specified element cannot be
         compared with the elements currently in the setNullPointerException - if the specified element is null
         and this set does not permit null elementsE higher(E e)
null if there is no such element.e - the value to matche,
         or null if there is no such elementClassCastException - if the specified element cannot be
         compared with the elements currently in the setNullPointerException - if the specified element is null
         and this set does not permit null elementsE pollFirst()
null if this set is empty.null if this set is emptyE pollLast()
null if this set is empty.null if this set is emptyIterator<E> iterator()
NavigableSet<E> descendingSet()
remove operation), the results of
 the iteration are undefined.
 The returned set has an ordering equivalent to
 Collections.reverseOrder(comparator()).
 The expression s.descendingSet().descendingSet() returns a
 view of s essentially equivalent to s.
Iterator<E> descendingIterator()
descendingSet().iterator().NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
fromElement to toElement.  If fromElement and
 toElement are equal, the returned set is empty unless fromInclusive and toInclusive are both true.  The returned set
 is backed by this set, so changes in the returned set are reflected in
 this set, and vice-versa.  The returned set supports all optional set
 operations that this set supports.
 The returned set will throw an IllegalArgumentException
 on an attempt to insert an element outside its range.
fromElement - low endpoint of the returned setfromInclusive - true if the low endpoint
        is to be included in the returned viewtoElement - high endpoint of the returned settoInclusive - true if the high endpoint
        is to be included in the returned viewfromElement, inclusive, to toElement, exclusiveClassCastException - if fromElement and
         toElement cannot be compared to one another using this
         set's comparator (or, if the set has no comparator, using
         natural ordering).  Implementations may, but are not required
         to, throw this exception if fromElement or
         toElement cannot be compared to elements currently in
         the set.NullPointerException - if fromElement or
         toElement is null and this set does
         not permit null elementsIllegalArgumentException - if fromElement is
         greater than toElement; or if this set itself
         has a restricted range, and fromElement or
         toElement lies outside the bounds of the range.NavigableSet<E> headSet(E toElement, boolean inclusive)
inclusive is true) toElement.  The
 returned set is backed by this set, so changes in the returned set are
 reflected in this set, and vice-versa.  The returned set supports all
 optional set operations that this set supports.
 The returned set will throw an IllegalArgumentException
 on an attempt to insert an element outside its range.
toElement - high endpoint of the returned setinclusive - true if the high endpoint
        is to be included in the returned viewinclusive is true) toElementClassCastException - if toElement is not compatible
         with this set's comparator (or, if the set has no comparator,
         if toElement does not implement Comparable).
         Implementations may, but are not required to, throw this
         exception if toElement cannot be compared to elements
         currently in the set.NullPointerException - if toElement is null and
         this set does not permit null elementsIllegalArgumentException - if this set itself has a
         restricted range, and toElement lies outside the
         bounds of the rangeNavigableSet<E> tailSet(E fromElement, boolean inclusive)
inclusive is true) fromElement.
 The returned set is backed by this set, so changes in the returned set
 are reflected in this set, and vice-versa.  The returned set supports
 all optional set operations that this set supports.
 The returned set will throw an IllegalArgumentException
 on an attempt to insert an element outside its range.
fromElement - low endpoint of the returned setinclusive - true if the low endpoint
        is to be included in the returned viewfromElementClassCastException - if fromElement is not compatible
         with this set's comparator (or, if the set has no comparator,
         if fromElement does not implement Comparable).
         Implementations may, but are not required to, throw this
         exception if fromElement cannot be compared to elements
         currently in the set.NullPointerException - if fromElement is null
         and this set does not permit null elementsIllegalArgumentException - if this set itself has a
         restricted range, and fromElement lies outside the
         bounds of the rangeSortedSet<E> subSet(E fromElement, E toElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to subSet(fromElement, true, toElement, false).
subSet in interface SortedSet<E>fromElement - low endpoint (inclusive) of the returned settoElement - high endpoint (exclusive) of the returned setClassCastException - if fromElement and
         toElement cannot be compared to one another using this
         set's comparator (or, if the set has no comparator, using
         natural ordering).  Implementations may, but are not required
         to, throw this exception if fromElement or
         toElement cannot be compared to elements currently in
         the set.NullPointerException - if fromElement or
         toElement is null and this set does not permit null
         elementsIllegalArgumentException - if fromElement is
         greater than toElement; or if this set itself
         has a restricted range, and fromElement or
         toElement lies outside the bounds of the rangeSortedSet<E> headSet(E toElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to headSet(toElement, false).
headSet in interface SortedSet<E>toElement - high endpoint (exclusive) of the returned setClassCastException - if toElement is not compatible
         with this set's comparator (or, if the set has no comparator,
         if toElement does not implement Comparable).
         Implementations may, but are not required to, throw this
         exception if toElement cannot be compared to elements
         currently in the set.NullPointerException - if toElement is null and
         this set does not permit null elementsIllegalArgumentException - if this set itself has a
         restricted range, and toElement lies outside the
         bounds of the rangeSortedSet<E> tailSet(E fromElement)
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
Equivalent to tailSet(fromElement, true).
tailSet in interface SortedSet<E>fromElement - low endpoint (inclusive) of the returned setClassCastException - if fromElement is not compatible
         with this set's comparator (or, if the set has no comparator,
         if fromElement does not implement Comparable).
         Implementations may, but are not required to, throw this
         exception if fromElement cannot be compared to elements
         currently in the set.NullPointerException - if fromElement is null
         and this set does not permit null elementsIllegalArgumentException - if this set itself has a
         restricted range, and fromElement lies outside the
         bounds of the range Submit a bug or feature 
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