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- Type Parameters:
E- the type of elements maintained by this set
- All Superinterfaces:
Collection<E>,Iterable<E>,Set<E>,SortedSet<E>
- All Known Implementing Classes:
ConcurrentSkipListSet,TreeSet
public interface NavigableSet<E> extends SortedSet<E>
ASortedSetextended with navigation methods reporting closest matches for given search targets. Methodslower(E),floor(E),ceiling(E), andhigher(E)return elements respectively less than, less than or equal, greater than or equal, and greater than a given element, returningnullif there is no such element.A
NavigableSetmay be accessed and traversed in either ascending or descending order. ThedescendingSet()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 methodspollFirst()andpollLast()that return and remove the lowest and highest element, if one exists, else returningnull. MethodssubSet(E, boolean, E, boolean),headSet(E, boolean), andtailSet(E, boolean)differ from the like-namedSortedSetmethods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Subsets of anyNavigableSetmust implement theNavigableSetinterface.The return values of navigation methods may be ambiguous in implementations that permit
nullelements. However, even in this case the result can be disambiguated by checkingcontains(null). To avoid such issues, implementations of this interface are encouraged to not permit insertion ofnullelements. (Note that sorted sets ofComparableelements intrinsically do not permitnull.)Methods
subSet(E, E),headSet(E), andtailSet(E)are specified to returnSortedSetto allow existing implementations ofSortedSetto be compatibly retrofitted to implementNavigableSet, but extensions and implementations of this interface are encouraged to override these methods to returnNavigableSet.This interface is a member of the Java Collections Framework.
- Since:
- 1.6
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description Eceiling(E e)Returns the least element in this set greater than or equal to the given element, ornullif 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.Efloor(E e)Returns the greatest element in this set less than or equal to the given element, ornullif there is no such element.SortedSet<E>headSet(E toElement)Returns a view of the portion of this set whose elements are strictly less thantoElement.NavigableSet<E>headSet(E toElement, boolean inclusive)Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusiveis true)toElement.Ehigher(E e)Returns the least element in this set strictly greater than the given element, ornullif there is no such element.Iterator<E>iterator()Returns an iterator over the elements in this set, in ascending order.Elower(E e)Returns the greatest element in this set strictly less than the given element, ornullif there is no such element.EpollFirst()Retrieves and removes the first (lowest) element, or returnsnullif this set is empty.EpollLast()Retrieves and removes the last (highest) element, or returnsnullif 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 fromfromElementtotoElement.SortedSet<E>subSet(E fromElement, E toElement)Returns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive.SortedSet<E>tailSet(E fromElement)Returns a view of the portion of this set whose elements are greater than or equal tofromElement.NavigableSet<E>tailSet(E fromElement, boolean inclusive)Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusiveis true)fromElement.-
Methods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArray
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Methods declared in interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
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Methods declared in interface java.util.SortedSet
comparator, first, last, spliterator
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Method Detail
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lower
E lower(E e)
Returns the greatest element in this set strictly less than the given element, ornullif there is no such element.- Parameters:
e- the value to match- Returns:
- the greatest element less than
e, ornullif there is no such element - Throws:
ClassCastException- 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 elements
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floor
E floor(E e)
Returns the greatest element in this set less than or equal to the given element, ornullif there is no such element.- Parameters:
e- the value to match- Returns:
- the greatest element less than or equal to
e, ornullif there is no such element - Throws:
ClassCastException- 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 elements
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ceiling
E ceiling(E e)
Returns the least element in this set greater than or equal to the given element, ornullif there is no such element.- Parameters:
e- the value to match- Returns:
- the least element greater than or equal to
e, ornullif there is no such element - Throws:
ClassCastException- 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 elements
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higher
E higher(E e)
Returns the least element in this set strictly greater than the given element, ornullif there is no such element.- Parameters:
e- the value to match- Returns:
- the least element greater than
e, ornullif there is no such element - Throws:
ClassCastException- 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 elements
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pollFirst
E pollFirst()
Retrieves and removes the first (lowest) element, or returnsnullif this set is empty.- Returns:
- the first element, or
nullif this set is empty
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pollLast
E pollLast()
Retrieves and removes the last (highest) element, or returnsnullif this set is empty.- Returns:
- the last element, or
nullif this set is empty
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iterator
Iterator<E> iterator()
Returns an iterator over the elements in this set, in ascending order.
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descendingSet
NavigableSet<E> descendingSet()
Returns a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa. If either set is modified while an iteration over either set is in progress (except through the iterator's ownremoveoperation), the results of the iteration are undefined.The returned set has an ordering equivalent to
Collections.reverseOrder(comparator()). The expressions.descendingSet().descendingSet()returns a view ofsessentially equivalent tos.- Returns:
- a reverse order view of this set
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descendingIterator
Iterator<E> descendingIterator()
Returns an iterator over the elements in this set, in descending order. Equivalent in effect todescendingSet().iterator().- Returns:
- an iterator over the elements in this set, in descending order
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subSet
NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range fromfromElementtotoElement. IffromElementandtoElementare equal, the returned set is empty unlessfromInclusiveandtoInclusiveare 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Parameters:
fromElement- low endpoint of the returned setfromInclusive-trueif the low endpoint is to be included in the returned viewtoElement- high endpoint of the returned settoInclusive-trueif the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements range from
fromElement, inclusive, totoElement, exclusive - Throws:
ClassCastException- iffromElementandtoElementcannot 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 iffromElementortoElementcannot be compared to elements currently in the set.NullPointerException- iffromElementortoElementis null and this set does not permit null elementsIllegalArgumentException- iffromElementis greater thantoElement; or if this set itself has a restricted range, andfromElementortoElementlies outside the bounds of the range.
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headSet
NavigableSet<E> headSet(E toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusiveis 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Parameters:
toElement- high endpoint of the returned setinclusive-trueif the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are less than
(or equal to, if
inclusiveis true)toElement - Throws:
ClassCastException- iftoElementis not compatible with this set's comparator (or, if the set has no comparator, iftoElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iftoElementcannot be compared to elements currently in the set.NullPointerException- iftoElementis null and this set does not permit null elementsIllegalArgumentException- if this set itself has a restricted range, andtoElementlies outside the bounds of the range
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tailSet
NavigableSet<E> tailSet(E fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusiveis 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Parameters:
fromElement- low endpoint of the returned setinclusive-trueif the low endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are greater
than or equal to
fromElement - Throws:
ClassCastException- iffromElementis not compatible with this set's comparator (or, if the set has no comparator, iffromElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iffromElementcannot be compared to elements currently in the set.NullPointerException- iffromElementis null and this set does not permit null elementsIllegalArgumentException- if this set itself has a restricted range, andfromElementlies outside the bounds of the range
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subSet
SortedSet<E> subSet(E fromElement, E toElement)
Returns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive. (IffromElementandtoElementare equal, the returned set is empty.) 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
subSet(fromElement, true, toElement, false).- Specified by:
subSetin interfaceSortedSet<E>- Parameters:
fromElement- low endpoint (inclusive) of the returned settoElement- high endpoint (exclusive) of the returned set- Returns:
- a view of the portion of this set whose elements range from
fromElement, inclusive, totoElement, exclusive - Throws:
ClassCastException- iffromElementandtoElementcannot 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 iffromElementortoElementcannot be compared to elements currently in the set.NullPointerException- iffromElementortoElementis null and this set does not permit null elementsIllegalArgumentException- iffromElementis greater thantoElement; or if this set itself has a restricted range, andfromElementortoElementlies outside the bounds of the range
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headSet
SortedSet<E> headSet(E toElement)
Returns a view of the portion of this set whose elements are strictly less thantoElement. 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
headSet(toElement, false).- Specified by:
headSetin interfaceSortedSet<E>- Parameters:
toElement- high endpoint (exclusive) of the returned set- Returns:
- a view of the portion of this set whose elements are strictly
less than
toElement - Throws:
ClassCastException- iftoElementis not compatible with this set's comparator (or, if the set has no comparator, iftoElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iftoElementcannot be compared to elements currently in the set.NullPointerException- iftoElementis null and this set does not permit null elementsIllegalArgumentException- if this set itself has a restricted range, andtoElementlies outside the bounds of the range
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tailSet
SortedSet<E> tailSet(E fromElement)
Returns a view of the portion of this set whose elements are greater than or equal tofromElement. 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
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
tailSet(fromElement, true).- Specified by:
tailSetin interfaceSortedSet<E>- Parameters:
fromElement- low endpoint (inclusive) of the returned set- Returns:
- a view of the portion of this set whose elements are greater
than or equal to
fromElement - Throws:
ClassCastException- iffromElementis not compatible with this set's comparator (or, if the set has no comparator, iffromElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iffromElementcannot be compared to elements currently in the set.NullPointerException- iffromElementis null and this set does not permit null elementsIllegalArgumentException- if this set itself has a restricted range, andfromElementlies outside the bounds of the range
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