edu.emory.mathcs.backport.java.util
Interface NavigableSet

All Superinterfaces:
java.util.Collection, java.util.Set, java.util.SortedSet
All Known Implementing Classes:
ConcurrentSkipListSet, TreeSet

public interface NavigableSet
extends java.util.SortedSet

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 viewed and traversed in either ascending or descending order. The Collection iterator method returns an ascending Iterator and the additional method descendingIterator returns a descending iterator. The performance of ascending traversals is likely to be faster than descending traversals. This interface additionally defines methods pollFirst and pollLast that return and remove the lowest and highest element, if one exists, else returning null. Methods navigableSubSet, navigableHeadSet, and navigableTailSet differ from the similarly named SortedSet methods only in their declared return types. 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.)

This interface is a member of the Java Collections Framework.

Since:
1.6
Author:
Doug Lea

Method Summary
 java.lang.Object ceiling(java.lang.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.
 java.util.Iterator descendingIterator()
          Returns an iterator over the elements in this set, in descending order.
 java.lang.Object floor(java.lang.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.
 java.lang.Object higher(java.lang.Object e)
          Returns the least element in this set strictly greater than the given element, or null if there is no such element.
 java.util.Iterator iterator()
          Returns an iterator over the elements in this set, in ascending order.
 java.lang.Object lower(java.lang.Object e)
          Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
 NavigableSet navigableHeadSet(java.lang.Object toElement)
          Returns a view of the portion of this set whose elements are strictly less than toElement.
 NavigableSet navigableSubSet(java.lang.Object fromElement, java.lang.Object toElement)
          Returns a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive.
 NavigableSet navigableTailSet(java.lang.Object fromElement)
          Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
 java.lang.Object pollFirst()
          Retrieves and removes the first (lowest) element, or returns null if this set is empty.
 java.lang.Object pollLast()
          Retrieves and removes the last (highest) element, or returns null if this set is empty.
 
Methods inherited from interface java.util.SortedSet
comparator, first, headSet, last, subSet, tailSet
 
Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray
 

Method Detail

lower

public java.lang.Object lower(java.lang.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
Throws:
java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set
java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

floor

public java.lang.Object floor(java.lang.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
Throws:
java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set
java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

ceiling

public java.lang.Object ceiling(java.lang.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
Throws:
java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set
java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

higher

public java.lang.Object higher(java.lang.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
Throws:
java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set
java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

pollFirst

public java.lang.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 java.lang.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

iterator

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

Specified by:
iterator in interface java.util.Set
Returns:
an iterator over the elements in this set, in ascending order

descendingIterator

public java.util.Iterator descendingIterator()
Returns an iterator over the elements in this set, in descending order.

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

navigableSubSet

public NavigableSet navigableSubSet(java.lang.Object fromElement,
                                    java.lang.Object toElement)
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.

Parameters:
fromElement - low endpoint (inclusive) of the returned set
toElement - high endpoint (exclusive) of the returned set
Returns:
a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive
Throws:
java.lang.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.
java.lang.NullPointerException - if fromElement or toElement is null and this set does not permit null elements
java.lang.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.

navigableHeadSet

public NavigableSet navigableHeadSet(java.lang.Object toElement)
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.

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:
java.lang.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.
java.lang.NullPointerException - if toElement is null and this set does not permit null elements
java.lang.IllegalArgumentException - if this set itself has a restricted range, and toElement lies outside the bounds of the range

navigableTailSet

public NavigableSet navigableTailSet(java.lang.Object fromElement)
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.

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:
java.lang.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.
java.lang.NullPointerException - if fromElement is null and this set does not permit null elements
java.lang.IllegalArgumentException - if this set itself has a restricted range, and fromElement lies outside the bounds of the range