java.util.NavigableSet

public interface java.util

NavigableSet<E>

Java SE 6

Implements: SortedSet

Implemented by: ConcurrentSkipListSet, TreeSet

A 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.

E the type of elements maintained by this set

since 1.6

Methods

public Object

ceiling(Object e) Details

Returns the least element in this set greater than or equal to the given element, or null if there is no such element.

e	the value to match
return	the least element greater than or equal to `e`, or `null` if there is no such element
Throws	ClassCastException: if the specified element cannot be compared with the elements currently in the set
Throws	NullPointerException: if the specified element is null and this set does not permit null elements

public Iterator

descendingIterator() Details

Returns an iterator over the elements in this set, in descending order. Equivalent in effect to descendingSet().iterator().

return

an iterator over the elements in this set, in descending order

public NavigableSet

descendingSet() Details

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 own 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.

return a reverse order view of this set

public Object

floor(Object e) Details

Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.

e	the value to match
return	the greatest element less than or equal to `e`, or `null` if there is no such element
Throws	ClassCastException: if the specified element cannot be compared with the elements currently in the set
Throws	NullPointerException: if the specified element is null and this set does not permit null elements

public NavigableSet

headSet(Object toElement, boolean inclusive) Details

Returns a view of the portion of this set whose elements are less than (or equal to, if 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 set

inclusive true if the high endpoint is to be included in the returned view

return a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement

Throws ClassCastException: 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.

Throws NullPointerException: if toElement is null and this set does not permit null elements

Throws IllegalArgumentException: if this set itself has a restricted range, and toElement lies outside the bounds of the range

public SortedSet

headSet(Object toElement) Details

Returns a view of the portion of this set whose elements are strictly less than 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.

Equivalent to headSet(toElement, false).

Throws ClassCastException: 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.

Throws NullPointerException: if toElement is null and this set does not permit null elements

Throws IllegalArgumentException: if this set itself has a restricted range, and toElement lies outside the bounds of the range na

public Object

higher(Object e) Details

Returns the least element in this set strictly greater than the given element, or null if there is no such element.

e	the value to match
return	the least element greater than `e`, or `null` if there is no such element
Throws	ClassCastException: if the specified element cannot be compared with the elements currently in the set
Throws	NullPointerException: if the specified element is null and this set does not permit null elements

public Iterator

iterator() Details

Returns an iterator over the elements in this set, in ascending order.

return

an iterator over the elements in this set, in ascending order

public Object

lower(Object e) Details

Returns the greatest element in this set strictly less than the given element, or null if there is no such element.

e	the value to match
return	the greatest element less than `e`, or `null` if there is no such element
Throws	ClassCastException: if the specified element cannot be compared with the elements currently in the set
Throws	NullPointerException: if the specified element is null and this set does not permit null elements

public Object

pollFirst() Details

Retrieves and removes the first (lowest) element, or returns null if this set is empty.

return the first element, or null if this set is empty

public Object

pollLast() Details

Retrieves and removes the last (highest) element, or returns null if this set is empty.

return the last element, or null if this set is empty

public NavigableSet

subSet(Object fromElement, boolean fromInclusive, Object toElement, boolean toInclusive) Details

Returns a view of the portion of this set whose elements range from fromElement to toElement. If fromElement and toElement are equal, the returned set is empty unless fromExclusive and toExclusive 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 set

fromInclusive true if the low endpoint is to be included in the returned view

toElement high endpoint of the returned set

toInclusive true if the high endpoint is to be included in the returned view

return a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive

Throws ClassCastException: 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.

Throws NullPointerException: if fromElement or toElement is null and this set does not permit null elements

Throws IllegalArgumentException: 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.

public SortedSet

subSet(Object fromElement, Object toElement) Details

Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive. (If fromElement and toElement are 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 IllegalArgumentException on an attempt to insert an element outside its range.

Equivalent to subSet(fromElement, true, toElement, false).

Throws ClassCastException: 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.

Throws NullPointerException: if fromElement or toElement is null and this set does not permit null elements

Throws IllegalArgumentException: 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

public NavigableSet

tailSet(Object fromElement, boolean inclusive) Details

Returns a view of the portion of this set whose elements are greater than (or equal to, if 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 set

inclusive true if the low endpoint is to be included in the returned view

return a view of the portion of this set whose elements are greater than or equal to fromElement

Throws ClassCastException: 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.

Throws NullPointerException: if fromElement is null and this set does not permit null elements

Throws IllegalArgumentException: if this set itself has a restricted range, and fromElement lies outside the bounds of the range

public SortedSet

tailSet(Object fromElement) Details

Returns a view of the portion of this set whose elements are greater than or equal to 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.

Equivalent to tailSet(fromElement, true).

Throws ClassCastException: 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.

Throws NullPointerException: if fromElement is null and this set does not permit null elements

Throws IllegalArgumentException: if this set itself has a restricted range, and fromElement lies outside the bounds of the range

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Java SE 6

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