edu.emory.mathcs.backport.java.util

Interface NavigableSet

All Superinterfaces:
SortedSet
Known Implementing Classes:
ConcurrentSkipListSet, TreeSet

public interface NavigableSet
extends SortedSet

A java.util.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 java.lang.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 ../../../../../../../technotes/guides/collections/index.html"> Java Collections Framework.

Authors:
Doug Lea
Josh Bloch
Since:
1.6

Method Summary

Object
ceiling(Object e)
Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
Iterator
descendingIterator()
Returns an iterator over the elements in this set, in descending order.
NavigableSet
descendingSet()
Returns a reverse order view of the elements contained in this set.
Object
floor(Object e)
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
SortedSet
headSet(Object toElement)
Equivalent to headSet(toElement, false).
NavigableSet
headSet(Object toElement, boolean inclusive)
Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement.
Object
higher(Object e)
Returns the least element in this set strictly greater than the given element, or null if there is no such element.
Iterator
iterator()
Returns an iterator over the elements in this set, in ascending order.
Object
lower(Object e)
Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
Object
pollFirst()
Retrieves and removes the first (lowest) element, or returns null if this set is empty.
Object
pollLast()
Retrieves and removes the last (highest) element, or returns null if this set is empty.
SortedSet
subSet(Object fromElement, Object toElement)
Equivalent to subSet(fromElement, true, toElement, false).
NavigableSet
subSet(Object fromElement, boolean fromInclusive, Object toElement, boolean toInclusive)
Returns a view of the portion of this set whose elements range from fromElement to toElement.
SortedSet
tailSet(Object fromElement)
Equivalent to tailSet(fromElement, true).
NavigableSet
tailSet(Object fromElement, boolean inclusive)
Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.

Method Details

ceiling

public Object ceiling(Object e)
Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
Parameters:
e - the value to match
Returns:
the least element greater than or equal to e, or null if there is no such element

descendingIterator

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

descendingSet

public NavigableSet 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 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.

Returns:
a reverse order view of this set

floor

public Object floor(Object e)
Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
Parameters:
e - the value to match
Returns:
the greatest element less than or equal to e, or null if there is no such element

headSet

public SortedSet headSet(Object toElement)
Equivalent to headSet(toElement, false).

headSet

public NavigableSet headSet(Object toElement,
                            boolean inclusive)
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.

Parameters:
toElement - high endpoint of the returned set
inclusive - true if 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 inclusive is true) toElement

higher

public Object higher(Object e)
Returns the least element in this set strictly greater than the given element, or null if there is no such element.
Parameters:
e - the value to match
Returns:
the least element greater than e, or null if there is no such element

iterator

public Iterator iterator()
Returns an iterator over the elements in this set, in ascending order.
Returns:
an iterator over the elements in this set, in ascending order

lower

public Object lower(Object e)
Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
Parameters:
e - the value to match
Returns:
the greatest element less than e, or null if there is no such element

pollFirst

public Object pollFirst()
Retrieves and removes the first (lowest) element, or returns null if this set is empty.
Returns:
the first element, or null if this set is empty

pollLast

public Object pollLast()
Retrieves and removes the last (highest) element, or returns null if this set is empty.
Returns:
the last element, or null if this set is empty

subSet

public SortedSet subSet(Object fromElement,
                        Object toElement)
Equivalent to subSet(fromElement, true, toElement, false).

subSet

public NavigableSet subSet(Object fromElement,
                           boolean fromInclusive,
                           Object toElement,
                           boolean toInclusive)
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.

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

tailSet

public SortedSet tailSet(Object fromElement)
Equivalent to tailSet(fromElement, true).

tailSet

public NavigableSet tailSet(Object fromElement,
                            boolean inclusive)
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.

Parameters:
fromElement - low endpoint of the returned set
inclusive - true if 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