ma.glasnost.orika.jsr166x

Class ConcurrentSkipListMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

ma.glasnost.orika.jsr166x.ConcurrentSkipListMap<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Implemented Interfaces:

Serializable, Cloneable, ConcurrentMap<K,V>, Map<K,V>, SortedMap<K,V>, ConcurrentNavigableMap<K,V>, NavigableMap<K,V>

public class ConcurrentSkipListMap<K,V>
extends AbstractMap<K,V>
implements ConcurrentNavigableMap<K,V>, Cloneable, Serializable

A scalable ConcurrentNavigableMap implementation. This class maintains a map in ascending key order, sorted according to the natural order for the key's class (see Comparable), or by the Comparator provided at creation time, depending on which constructor is used.

This class implements a concurrent variant of SkipLists providing expected average log(n) time cost for the containsKey, get, put and remove operations and their variants. Insertion, removal, update, and access operations safely execute concurrently by multiple threads. Iterators are weakly consistent, returning elements reflecting the state of the map at some point at or since the creation of the iterator. They do not throw ConcurrentModificationException, and may proceed concurrently with other operations. Ascending key ordered views and their iterators are faster than descending ones.

All Map.Entry pairs returned by methods in this class and its views represent snapshots of mappings at the time they were produced. They do not support the Entry.setValue method. (Note however that it is possible to change mappings in the associated map using put, putIfAbsent, or replace, depending on exactly which effect you need.)

Beware that, unlike in most collections, the size method is not a constant-time operation. Because of the asynchronous nature of these maps, determining the current number of elements requires a traversal of the elements. Additionally, the bulk operations putAll, equals, and clear are not guaranteed to be performed atomically. For example, an iterator operating concurrently with a putAll operation might view only some of the added elements.

This class and its views and iterators implement all of the optional methods of the Map and Iterator interfaces. Like most other concurrent collections, this class does not permit the use of null keys or values because some null return values cannot be reliably distinguished from the absence of elements.

Author:

Doug Lea

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
ConcurrentSkipListMap() Constructs a new empty map, sorted according to the keys' natural order.
ConcurrentSkipListMap(Comparator<? super K> c) Constructs a new empty map, sorted according to the given comparator.
ConcurrentSkipListMap(Map<? extends K,? extends V> m) Constructs a new map containing the same mappings as the given map, sorted according to the keys' natural order.
ConcurrentSkipListMap(SortedMap<K,? extends V> m) Constructs a new map containing the same mappings as the given SortedMap, sorted according to the same ordering.

Method Summary

Modifier and Type	Method and Description
Map.Entry<K,V>	ceilingEntry(K key) Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such entry.
K	ceilingKey(K key) Returns least key greater than or equal to the given key, or null if there is no such key.
void	clear() Removes all mappings from this map.
Object	clone() Returns a shallow copy of this Map instance.
Comparator<? super K>	comparator() Returns the comparator used to order this map, or null if this map uses its keys' natural order.
boolean	containsKey(Object key) Returns true if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns true if this map maps one or more keys to the specified value.
Set<Map.Entry<K,V>>	descendingEntrySet() Returns a collection view of the mappings contained in this map, in descending order.
Set<K>	descendingKeySet() Returns a set view of the keys contained in this map in descending order.
Set<Map.Entry<K,V>>	entrySet() Returns a collection view of the mappings contained in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
Map.Entry<K,V>	firstEntry() Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
K	firstKey() Returns the first (lowest) key currently in this map.
Map.Entry<K,V>	floorEntry(K key) Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such entry.
K	floorKey(K key) Returns the greatest key less than or equal to the given key, or null if there is no such key.
V	get(Object key) Returns the value to which this map maps the specified key.
ConcurrentNavigableMap<K,V>	headMap(K toKey) Returns a view of the portion of this map whose keys are strictly less than toKey.
Map.Entry<K,V>	higherEntry(K key) Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such entry.
K	higherKey(K key) Returns the least key strictly greater than the given key, or null if there is no such key.
boolean	isEmpty() Returns true if this map contains no key-value mappings.
Set<K>	keySet() Returns a set view of the keys contained in this map.
Map.Entry<K,V>	lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
K	lastKey() Returns the last (highest) key currently in this map.
Map.Entry<K,V>	lowerEntry(K key) Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such entry.
K	lowerKey(K key) Returns the greatest key strictly less than the given key, or null if there is no such key.
Map.Entry<K,V>	pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
Map.Entry<K,V>	pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
V	put(K key, V value) Associates the specified value with the specified key in this map.
V	putIfAbsent(K key, V value) If the specified key is not already associated with a value, associate it with the given value.
V	remove(Object key) Removes the mapping for this key from this Map if present.
boolean	remove(Object key, Object value) Remove entry for key only if currently mapped to given value.
V	replace(K key, V value) Replace entry for key only if currently mapped to some value.
boolean	replace(K key, V oldValue, V newValue) Replace entry for key only if currently mapped to given value.
int	size() Returns the number of elements in this map.
ConcurrentNavigableMap<K,V>	subMap(K fromKey, K toKey) Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.
ConcurrentNavigableMap<K,V>	tailMap(K fromKey) Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
Collection<V>	values() Returns a collection view of the values contained in this map.

Methods inherited from class java.util.AbstractMap

hashCode, putAll, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.concurrent.ConcurrentMap

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAll

Methods inherited from interface java.util.Map

hashCode, putAll

Constructor Detail

ConcurrentSkipListMap

public ConcurrentSkipListMap()

Constructs a new empty map, sorted according to the keys' natural order.

ConcurrentSkipListMap

public ConcurrentSkipListMap(Comparator<? super K> c)

Constructs a new empty map, sorted according to the given comparator.

Parameters:

c - the comparator that will be used to sort this map. A null value indicates that the keys' natural ordering should be used.

ConcurrentSkipListMap

public ConcurrentSkipListMap(Map<? extends K,? extends V> m)

Constructs a new map containing the same mappings as the given map, sorted according to the keys' natural order.

Parameters:

m - the map whose mappings are to be placed in this map.

Throws:

ClassCastException - if the keys in m are not Comparable, or are not mutually comparable.

NullPointerException - if the specified map is null.

ConcurrentSkipListMap

public ConcurrentSkipListMap(SortedMap<K,? extends V> m)

Constructs a new map containing the same mappings as the given SortedMap, sorted according to the same ordering.

Parameters:

m - the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map.

Throws:

NullPointerException - if the specified sorted map is null.

Method Detail

clone

public Object clone()

Returns a shallow copy of this Map instance. (The keys and values themselves are not cloned.)

Overrides:

clone in class AbstractMap<K,V>

Returns:

a shallow copy of this Map.

containsKey

public boolean containsKey(Object key)

Returns true if this map contains a mapping for the specified key.

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

Parameters:

key - key whose presence in this map is to be tested.

Returns:

true if this map contains a mapping for the specified key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key is null.

get

public V get(Object key)

Returns the value to which this map maps the specified key. Returns null if the map contains no mapping for this key.

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

Parameters:

key - key whose associated value is to be returned.

Returns:

the value to which this map maps the specified key, or null if the map contains no mapping for the key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key is null.

put

public V put(K key,
             V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key or value are null.

remove

public V remove(Object key)

Removes the mapping for this key from this Map if present.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>

Parameters:

key - key for which mapping should be removed

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key is null.

containsValue

public boolean containsValue(Object value)

Returns true if this map maps one or more keys to the specified value. This operation requires time linear in the Map size.

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class AbstractMap<K,V>

Parameters:

value - value whose presence in this Map is to be tested.

Returns:

true if a mapping to value exists; false otherwise.

Throws:

NullPointerException - if the value is null.

size

public int size()

Returns the number of elements in this map. If this map contains more than Integer.MAX_VALUE elements, it returns Integer.MAX_VALUE.

Beware that, unlike in most collections, this method is NOT a constant-time operation. Because of the asynchronous nature of these maps, determining the current number of elements requires traversing them all to count them. Additionally, it is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

Returns:

the number of elements in this map.

isEmpty

public boolean isEmpty()

Returns true if this map contains no key-value mappings.

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractMap<K,V>

Returns:

true if this map contains no key-value mappings.

clear

public void clear()

Removes all mappings from this map.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class AbstractMap<K,V>

keySet

public Set<K> keySet()

Returns a set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations. The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

Specified by:

keySet in interface Map<K,V>

Specified by:

keySet in interface SortedMap<K,V>

Overrides:

keySet in class AbstractMap<K,V>

Returns:

a set view of the keys contained in this map.

descendingKeySet

public Set<K> descendingKeySet()

Returns a set view of the keys contained in this map in descending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations. The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

Specified by:

descendingKeySet in interface NavigableMap<K,V>

Returns:

a set view of the keys contained in this map.

values

public Collection<V> values()

Returns a collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations. The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.

Specified by:

values in interface Map<K,V>

Specified by:

values in interface SortedMap<K,V>

Overrides:

values in class AbstractMap<K,V>

Returns:

a collection view of the values contained in this map.

entrySet

public Set<Map.Entry<K,V>> entrySet()

Returns a collection view of the mappings contained in this map. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations. The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction. The Map.Entry elements returned by iterator.next() do not support the setValue operation.

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in interface SortedMap<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

Returns:

a collection view of the mappings contained in this map.

descendingEntrySet

public Set<Map.Entry<K,V>> descendingEntrySet()

Returns a collection view of the mappings contained in this map, in descending order. Each element in the returned collection is a Map.Entry. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations. The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction. The Map.Entry elements returned by iterator.next() do not support the setValue operation.

Specified by:

descendingEntrySet in interface NavigableMap<K,V>

Returns:

a collection view of the mappings contained in this map.

equals

public boolean equals(Object o)

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps t1 and t2 represent the same mappings if t1.keySet().equals(t2.keySet()) and for every key k in t1.keySet(), (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))) . This operation may return misleading results if either map is concurrently modified during execution of this method.

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class AbstractMap<K,V>

Parameters:

o - object to be compared for equality with this map.

Returns:

true if the specified object is equal to this map.

putIfAbsent

public V putIfAbsent(K key,
                     V value)

If the specified key is not already associated with a value, associate it with the given value. This is equivalent to

   if (!map.containsKey(key))
      return map.put(key, value);
   else
      return map.get(key);
 

except that the action is performed atomically.

Specified by:

putIfAbsent in interface ConcurrentMap<K,V>

Specified by:

putIfAbsent in interface Map<K,V>

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key or value are null.

remove

public boolean remove(Object key,
                      Object value)

Remove entry for key only if currently mapped to given value. Acts as

  if ((map.containsKey(key) && map.get(key).equals(value)) {
     map.remove(key);
     return true;
 } else return false;
 

except that the action is performed atomically.

Specified by:

remove in interface ConcurrentMap<K,V>

Specified by:

remove in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

value - value associated with the specified key.

Returns:

true if the value was removed, false otherwise

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key or value are null.

replace

public boolean replace(K key,
                       V oldValue,
                       V newValue)

Replace entry for key only if currently mapped to given value. Acts as

  if ((map.containsKey(key) && map.get(key).equals(oldValue)) {
     map.put(key, newValue);
     return true;
 } else return false;
 

except that the action is performed atomically.

Specified by:

replace in interface ConcurrentMap<K,V>

Specified by:

replace in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

oldValue - value expected to be associated with the specified key.

newValue - value to be associated with the specified key.

Returns:

true if the value was replaced

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if key, oldValue or newValue are null.

replace

public V replace(K key,
                 V value)

Replace entry for key only if currently mapped to some value. Acts as

  if ((map.containsKey(key)) {
     return map.put(key, value);
 } else return null;
 

except that the action is performed atomically.

Specified by:

replace in interface ConcurrentMap<K,V>

Specified by:

replace in interface Map<K,V>

Parameters:

key - key with which the specified value is associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key.

Throws:

ClassCastException - if the key cannot be compared with the keys currently in the map.

NullPointerException - if the key or value are null.

comparator

public Comparator<? super K> comparator()

Returns the comparator used to order this map, or null if this map uses its keys' natural order.

Specified by:

comparator in interface SortedMap<K,V>

Returns:

the comparator associated with this map, or null if it uses its keys' natural sort method.

firstKey

public K firstKey()

Returns the first (lowest) key currently in this map.

Specified by:

firstKey in interface SortedMap<K,V>

Returns:

the first (lowest) key currently in this map.

Throws:

NoSuchElementException - Map is empty.

lastKey

public K lastKey()

Returns the last (highest) key currently in this map.

Specified by:

lastKey in interface SortedMap<K,V>

Returns:

the last (highest) key currently in this map.

Throws:

NoSuchElementException - Map is empty.

subMap

public ConcurrentNavigableMap<K,V> subMap(K fromKey,
                                          K toKey)

Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned sorted map is empty.) The returned sorted map is backed by this map, so changes in the returned sorted map are reflected in this map, and vice-versa.

Specified by:

subMap in interface SortedMap<K,V>

Specified by:

subMap in interface ConcurrentNavigableMap<K,V>

Specified by:

subMap in interface NavigableMap<K,V>

Parameters:

fromKey - low endpoint (inclusive) of the subMap.

toKey - high endpoint (exclusive) of the subMap.

Returns:

a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive.

Throws:

ClassCastException - if fromKey and toKey cannot be compared to one another using this map's comparator (or, if the map has no comparator, using natural ordering).

IllegalArgumentException - if fromKey is greater than toKey.

NullPointerException - if fromKey or toKey is null.

headMap

public ConcurrentNavigableMap<K,V> headMap(K toKey)

Returns a view of the portion of this map whose keys are strictly less than toKey. The returned sorted map is backed by this map, so changes in the returned sorted map are reflected in this map, and vice-versa.

Specified by:

headMap in interface SortedMap<K,V>

Specified by:

headMap in interface ConcurrentNavigableMap<K,V>

Specified by:

headMap in interface NavigableMap<K,V>

Parameters:

toKey - high endpoint (exclusive) of the headMap.

Returns:

a view of the portion of this map whose keys are strictly less than toKey.

Throws:

ClassCastException - if toKey is not compatible with this map's comparator (or, if the map has no comparator, if toKey does not implement Comparable).

NullPointerException - if toKey is null.

tailMap

public ConcurrentNavigableMap<K,V> tailMap(K fromKey)

Returns a view of the portion of this map whose keys are greater than or equal to fromKey. The returned sorted map is backed by this map, so changes in the returned sorted map are reflected in this map, and vice-versa.

Specified by:

tailMap in interface SortedMap<K,V>

Specified by:

tailMap in interface ConcurrentNavigableMap<K,V>

Specified by:

tailMap in interface NavigableMap<K,V>

Parameters:

fromKey - low endpoint (inclusive) of the tailMap.

Returns:

a view of the portion of this map whose keys are greater than or equal to fromKey.

Throws:

ClassCastException - if fromKey is not compatible with this map's comparator (or, if the map has no comparator, if fromKey does not implement Comparable).

NullPointerException - if fromKey is null.

ceilingEntry

public Map.Entry<K,V> ceilingEntry(K key)

Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such entry. The returned entry does not support the Entry.setValue method.

Specified by:

ceilingEntry in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

an Entry associated with ceiling of given key, or null if there is no such Entry.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

ceilingKey

public K ceilingKey(K key)

Returns least key greater than or equal to the given key, or null if there is no such key.

Specified by:

ceilingKey in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

the ceiling key, or null if there is no such key.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

lowerEntry

public Map.Entry<K,V> lowerEntry(K key)

Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such entry. The returned entry does not support the Entry.setValue method.

Specified by:

lowerEntry in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

an Entry with greatest key less than the given key, or null if there is no such Entry.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

lowerKey

public K lowerKey(K key)

Returns the greatest key strictly less than the given key, or null if there is no such key.

Specified by:

lowerKey in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

the greatest key less than the given key, or null if there is no such key.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

floorEntry

public Map.Entry<K,V> floorEntry(K key)

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such entry. The returned entry does not support the Entry.setValue method.

Specified by:

floorEntry in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

an Entry associated with floor of given key, or null if there is no such Entry.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

floorKey

public K floorKey(K key)

Returns the greatest key less than or equal to the given key, or null if there is no such key.

Specified by:

floorKey in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

the floor of given key, or null if there is no such key.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

higherEntry

public Map.Entry<K,V> higherEntry(K key)

Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such entry. The returned entry does not support the Entry.setValue method.

Specified by:

higherEntry in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

an Entry with least key greater than the given key, or null if there is no such Entry.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

higherKey

public K higherKey(K key)

Returns the least key strictly greater than the given key, or null if there is no such key.

Specified by:

higherKey in interface NavigableMap<K,V>

Parameters:

key - the key.

Returns:

the least key greater than the given key, or null if there is no such key.

Throws:

ClassCastException - if key cannot be compared with the keys currently in the map.

NullPointerException - if key is null.

firstEntry

public Map.Entry<K,V> firstEntry()

Returns a key-value mapping associated with the least key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

firstEntry in interface NavigableMap<K,V>

Returns:

an Entry with least key, or null if the map is empty.

lastEntry

public Map.Entry<K,V> lastEntry()

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

lastEntry in interface NavigableMap<K,V>

Returns:

an Entry with greatest key, or null if the map is empty.

pollFirstEntry

public Map.Entry<K,V> pollFirstEntry()

Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

pollFirstEntry in interface NavigableMap<K,V>

Returns:

the removed first entry of this map, or null if the map is empty.

pollLastEntry

public Map.Entry<K,V> pollLastEntry()

Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. The returned entry does not support the Entry.setValue method.

Specified by:

pollLastEntry in interface NavigableMap<K,V>

Returns:

the removed last entry of this map, or null if the map is empty.