NavigableSet

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
```
public interface NavigableSet<E>
extends SortedSet<E>
```
A SortedSet extended with navigation methods reporting closest matches for given search targets. Methods lower, floor, ceiling, and higher return keys respectively less than, less than or equal, greater than or equal, and greater than a given key, returning null if there is no such key. 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 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 key, if one exists, else returning null.
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 not to permit insertion of null elements. (Note that sorted sets of Comparable elements intrinsically do not permit null.)

Author:

Doug Lea

Method Summary

Methods
Modifier and Type	Method and Description
`E`	`ceiling(E o)` Returns an element greater than or equal to the given element, or `null` if there is no such element.
`Iterator<E>`	`descendingIterator()` Returns an iterator over the elements in this collection, in descending order.
`E`	`floor(E o)` Returns an element less than or equal to the given element, or `null` if there is no such element.
`NavigableSet<E>`	`headSet(E toElement)` Returns a view of the portion of this set whose elements are strictly less than `toElement`.
`E`	`higher(E o)` Returns an element strictly greater than the given element, or `null` if there is no such element.
`E`	`lower(E o)` Returns an element strictly less than the given element, or `null` if there is no such element.
`E`	`pollFirst()` Retrieves and removes the first (lowest) element.
`E`	`pollLast()` Retrieves and removes the last (highest) element.
`NavigableSet<E>`	`subSet(E fromElement, E toElement)` Returns a view of the portion of this set whose elements range from `fromElement`, inclusive, to `toElement`, exclusive.
`NavigableSet<E>`	`tailSet(E fromElement)` Returns a view of the portion of this set whose elements are greater than or equal to `fromElement`.

Methods inherited from interface java.util.SortedSet
comparator, first, last

Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

- Method Detail
  - ceiling
```
E ceiling(E o)
```
    Returns an element greater than or equal to the given element, or null if there is no such element.
    
    Parameters:
    o - the value to match
    
    Returns:
    an element greater than or equal to given element, or null if there is no such element
    
    Throws:
    
    ClassCastException - if o cannot be compared with the elements currently in the set
    
    NullPointerException - if o is null and this set deas not permit null elements
  - lower
```
E lower(E o)
```
    Returns an element strictly less than the given element, or null if there is no such element.
    
    Parameters:
    o - the value to match
    
    Returns:
    the greatest element less than the given element, or null if there is no such element
    
    Throws:
    
    ClassCastException - if o cannot be compared with the elements currently in the set
    
    NullPointerException - if o is null and this set deas not permit null elements
  - floor
```
E floor(E o)
```
    Returns an element less than or equal to the given element, or null if there is no such element.
    
    Parameters:
    o - the value to match
    
    Returns:
    the greatest element less than or equal to given element, or null if there is no such element
    
    Throws:
    
    ClassCastException - if o cannot be compared with the elements currently in the set
    
    NullPointerException - if o is null and this set deas not permit null elements
  - higher
```
E higher(E o)
```
    Returns an element strictly greater than the given element, or null if there is no such element.
    
    Parameters:
    o - the value to match
    
    Returns:
    the least element greater than the given element, or null if there is no such element
    
    Throws:
    
    ClassCastException - if o cannot be compared with the elements currently in the set
    
    NullPointerException - if o is null and this set deas not permit null elements
  - pollFirst
```
E pollFirst()
```
    Retrieves and removes the first (lowest) element.
    
    Returns:
    the first element, or null if empty
  - pollLast
```
E pollLast()
```
    Retrieves and removes the last (highest) element.
    
    Returns:
    the last element, or null if empty
  - descendingIterator
```
Iterator<E> descendingIterator()
```
    Returns an iterator over the elements in this collection, in descending order.
    
    Returns:
    an Iterator over the elements in this collection
  - subSet
```
NavigableSet<E> subSet(E fromElement,
                     E 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 sorted set is empty.) The returned sorted set is backed by this set, so changes in the returned sorted set are reflected in this set, and vice-versa.
    
    Specified by:
    
    subSet in interface SortedSet<E>
    
    Parameters:
    fromElement - low endpoint (inclusive) of the subSet
    toElement - high endpoint (exclusive) of the subSet
    
    Returns:
    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)
    
    IllegalArgumentException - if fromElement is greater than toElement
    
    NullPointerException - if fromElement or toElement is null and this set deas not permit null elements
  - headSet
```
NavigableSet<E> headSet(E toElement)
```
    Returns a view of the portion of this set whose elements are strictly less than toElement. The returned sorted set is backed by this set, so changes in the returned sorted set are reflected in this set, and vice-versa.
    
    Specified by:
    
    headSet in interface SortedSet<E>
    
    Parameters:
    toElement - high endpoint (exclusive) of the headSet
    
    Returns:
    a view of the portion of this set whose elements are strictly less than 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)
    
    NullPointerException - if toElement is null and this set deas not permit null elements
  - tailSet
```
NavigableSet<E> tailSet(E fromElement)
```
    Returns a view of the portion of this set whose elements are greater than or equal to fromElement. The returned sorted set is backed by this set, so changes in the returned sorted set are reflected in this set, and vice-versa.
    
    Specified by:
    
    tailSet in interface SortedSet<E>
    
    Parameters:
    fromElement - low endpoint (inclusive) of the tailSet
    
    Returns:
    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)
    
    NullPointerException - if fromElement is null and this set deas not permit null elements

Interface NavigableSet<E>

Method Summary

Methods inherited from interface java.util.SortedSet

Methods inherited from interface java.util.Set

Method Detail

ceiling

lower

floor

higher

pollFirst

pollLast

descendingIterator

subSet

headSet

tailSet