Package java.util.concurrent

Class ConcurrentSkipListMap<K,​V>

java.lang.Object
java.util.AbstractMap<K,​V>
java.util.concurrent.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>, ConcurrentNavigableMap<K,​V>, Map<K,​V>, NavigableMap<K,​V>, SortedMap<K,​V>
public class ConcurrentSkipListMap<K,​V>
extends AbstractMap<K,​V>
implements ConcurrentNavigableMap<K,​V>, Cloneable, Serializable
A scalable concurrent ConcurrentNavigableMap implementation. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map 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, and so may report inaccurate results if this collection is modified during traversal. Additionally, the bulk operations putAll, equals, toArray, containsValue, 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.

Since:
1.6
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 Description
    ConcurrentSkipListMap()
    Constructs a new, empty map, sorted according to the natural ordering of the keys.
    ConcurrentSkipListMap​(Comparator<? super K> comparator)
    Constructs a new, empty map, sorted according to the specified comparator.
    ConcurrentSkipListMap​(Map<? extends K,​? extends V> m)
    Constructs a new map containing the same mappings as the given map, sorted according to the natural ordering of the keys.
    ConcurrentSkipListMap​(SortedMap<K,​? extends V> m)
    Constructs a new map containing the same mappings and using the same ordering as the specified sorted map.

  • Method Summary

    Modifier and Type Method 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 the least key greater than or equal to the given key, or null if there is no such key.
    void clear()
    Removes all of the mappings from this map.
    ConcurrentSkipListMap<K,​V> clone()
    Returns a shallow copy of this ConcurrentSkipListMap instance.
    Comparator<? super K> comparator()
    Returns the comparator used to compare keys in this sorted map, or null if the natural ordering is in use.
    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.
    NavigableSet<K> descendingKeySet()
    Returns a reverse order NavigableSet view of the keys contained in this map.
    ConcurrentNavigableMap<K,​V> descendingMap()
    Returns a reverse order view of the mappings contained in this map.
    Set<Map.Entry<K,​V>> entrySet()
    Returns a Set 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 least key in this sorted 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 key.
    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 the specified key is mapped, or null if this map contains no mapping for the key.
    ConcurrentNavigableMap<K,​V> headMap​(K toKey)
    Returns a sorted map over a range of this sorted map with all keys that are less than the specified endKey.
    ConcurrentNavigableMap<K,​V> headMap​(K toKey, boolean inclusive)
    Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) 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 key.
    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.
    NavigableSet<K> keySet()
    Returns a NavigableSet 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 greatest key in this sorted 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 key.
    K lowerKey​(K key)
    Returns the greatest key strictly less than the given key, or null if there is no such key.
    NavigableSet<K> navigableKeySet()
    Returns a NavigableSet view of the keys contained in this map.
    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 the specified key from this map if present.
    boolean remove​(Object key, Object value)
    Removes the entry for a key only if currently mapped to a given value.
    V replace​(K key, V value)
    Replaces the entry for a key only if currently mapped to some value.
    boolean replace​(K key, V oldValue, V newValue)
    Replaces the entry for a key only if currently mapped to a given value.
    int size()
    Returns the number of key-value mappings in this map.
    ConcurrentNavigableMap<K,​V> subMap​(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
    Returns a view of the portion of this map whose keys range from fromKey to toKey.
    ConcurrentNavigableMap<K,​V> subMap​(K fromKey, K toKey)
    Returns a sorted map over a range of this sorted map with all keys greater than or equal to the specified startKey and less than the specified endKey.
    ConcurrentNavigableMap<K,​V> tailMap​(K fromKey)
    Returns a sorted map over a range of this sorted map with all keys that are greater than or equal to the specified startKey.
    ConcurrentNavigableMap<K,​V> tailMap​(K fromKey, boolean inclusive)
    Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) 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.Map

    hashCode, putAll

  • Constructor Details

    • ConcurrentSkipListMap

      public ConcurrentSkipListMap()
      Constructs a new, empty map, sorted according to the natural ordering of the keys.

    • ConcurrentSkipListMap

      public ConcurrentSkipListMap​(Comparator<? super K> comparator)
      Constructs a new, empty map, sorted according to the specified comparator.
      Parameters:
      comparator - the comparator that will be used to order this map. If null, the natural ordering of the keys will 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 natural ordering of the keys.
      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 or any of its keys or values are null

    • ConcurrentSkipListMap

      public ConcurrentSkipListMap​(SortedMap<K,​? extends V> m)
      Constructs a new map containing the same mappings and using the same ordering as the specified sorted map.
      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 or any of its keys or values are null

  • Method Details

    • clone

      public ConcurrentSkipListMap<K,​V> clone()
      Returns a shallow copy of this ConcurrentSkipListMap 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 specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • get

      public V get​(Object key)
      Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

      More formally, if this map contains a mapping from a key k to a value v such that key compares equal to k according to the map's ordering, then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

      Specified by:
      get in interface Map<K,​V>
      Overrides:
      get in class AbstractMap<K,​V>
      Parameters:
      key - the key.
      Returns:
      the value of the mapping with the specified key, or null if no mapping for the specified key is found.
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified 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 the 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:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key or value is null

    • remove

      public V remove​(Object key)
      Removes the mapping for the specified 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:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified 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. Additionally, it is possible for the map to change during execution of this method, in which case the returned result may be inaccurate.
      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 specified value is null

    • size

      public int size()
      Returns the number of key-value mappings 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
      See Also:
      Map.size()

    • clear

      public void clear()
      Removes all of the mappings from this map.
      Specified by:
      clear in interface Map<K,​V>
      Overrides:
      clear in class AbstractMap<K,​V>
      See Also:
      Map.isEmpty(), Map.size()

    • keySet

      public NavigableSet<K> keySet()
      Returns a NavigableSet view of the keys contained in this map. The set's iterator returns the keys in ascending 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 the 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.

      This method is equivalent to method navigableKeySet.

      Specified by:
      keySet in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      keySet in interface Map<K,​V>
      Overrides:
      keySet in class AbstractMap<K,​V>
      Returns:
      a navigable set view of the keys in this map

    • values

      public Collection<V> values()
      Returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. 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.

      Specified by:
      values in interface Map<K,​V>
      Overrides:
      values in class AbstractMap<K,​V>
      Returns:
      a collection of the values contained in this map.

    • entrySet

      public Set<Map.Entry<K,​V>> entrySet()
      Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in ascending key 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 the 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.

      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 class AbstractMap<K,​V>
      Returns:
      a set view of the mappings contained in this map, sorted in ascending key order

    • descendingMap

      public ConcurrentNavigableMap<K,​V> descendingMap()
      Description copied from interface: ConcurrentNavigableMap
      Returns a reverse order view of the mappings contained in this map. The descending map is backed by this map, so changes to the map are reflected in the descending map, and vice-versa.

      The returned map has an ordering equivalent to Collections.reverseOrder(comparator()). The expression m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.

      Specified by:
      descendingMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      descendingMap in interface NavigableMap<K,​V>
      Returns:
      a reverse order view of this map

    • descendingKeySet

      public NavigableSet<K> descendingKeySet()
      Description copied from interface: ConcurrentNavigableMap
      Returns a reverse order NavigableSet view of the keys contained in this map. The set's iterator returns the keys 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 the 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 ConcurrentNavigableMap<K,​V>
      Specified by:
      descendingKeySet in interface NavigableMap<K,​V>
      Returns:
      a reverse order navigable set view of the keys 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 m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). 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
      See Also:
      Object.hashCode()

    • 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>
      Parameters:
      key - key with which the specified value is to be associated
      value - value to be associated with the specified key
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key or value is null

    • remove

      public boolean remove​(Object key, Object value)
      Removes the entry for a key only if currently mapped to a given value. This is equivalent to 
       
 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>
      Parameters:
      key - key with which the specified value is associated
      value - value expected to be associated with the specified key
      Returns:
      true if the value was removed
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • replace

      public boolean replace​(K key, V oldValue, V newValue)
      Replaces the entry for a key only if currently mapped to a given value. This is equivalent to 
       
 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>
      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 specified key cannot be compared with the keys currently in the map
      NullPointerException - if any of the arguments are null

    • replace

      public V replace​(K key, V value)
      Replaces the entry for a key only if currently mapped to some value. This is equivalent to 
       
 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>
      Parameters:
      key - key with which the specified value is associated
      value - value to be associated with the specified key
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key or value is null

    • comparator

      public Comparator<? super K> comparator()
      Description copied from interface: SortedMap
      Returns the comparator used to compare keys in this sorted map, or null if the natural ordering is in use.
      Specified by:
      comparator in interface SortedMap<K,​V>

    • firstKey

      public K firstKey()
      Description copied from interface: SortedMap
      Returns the least key in this sorted map.
      Specified by:
      firstKey in interface SortedMap<K,​V>
      Throws:
      NoSuchElementException - if this sorted map is empty.

    • lastKey

      public K lastKey()
      Description copied from interface: SortedMap
      Returns the greatest key in this sorted map.
      Specified by:
      lastKey in interface SortedMap<K,​V>
      Throws:
      NoSuchElementException - if this sorted map is empty.

    • subMap

      public ConcurrentNavigableMap<K,​V> subMap​(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)
      Description copied from interface: NavigableMap
      Returns a view of the portion of this map whose keys range from fromKey to toKey. If fromKey and toKey are equal, the returned map is empty unless fromExclusive and toExclusive are both true. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

      The returned map will throw an IllegalArgumentException on an attempt to insert a key outside of its range, or to construct a submap either of whose endpoints lie outside its range.

      Specified by:
      subMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      subMap in interface NavigableMap<K,​V>
      Parameters:
      fromKey - low endpoint of the keys in the returned map
      fromInclusive - true if the low endpoint is to be included in the returned view
      toKey - high endpoint of the keys in the returned map
      toInclusive - true if the high endpoint is to be included in the returned view
      Returns:
      a view of the portion of this map whose keys range from fromKey to toKey
      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). Implementations may, but are not required to, throw this exception if fromKey or toKey cannot be compared to keys currently in the map.
      NullPointerException - if fromKey or toKey is null
      IllegalArgumentException - if fromKey is greater than toKey; or if this map itself has a restricted range, and fromKey or toKey lies outside the bounds of the range

    • headMap

      public ConcurrentNavigableMap<K,​V> headMap​(K toKey, boolean inclusive)
      Description copied from interface: NavigableMap
      Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

      The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

      Specified by:
      headMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      headMap in interface NavigableMap<K,​V>
      Parameters:
      toKey - high endpoint of the keys in the returned map
      inclusive - true if the high endpoint is to be included in the returned view
      Returns:
      a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) 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). Implementations may, but are not required to, throw this exception if toKey cannot be compared to keys currently in the map.
      NullPointerException - if toKey is null
      IllegalArgumentException - if this map itself has a restricted range, and toKey lies outside the bounds of the range

    • tailMap

      public ConcurrentNavigableMap<K,​V> tailMap​(K fromKey, boolean inclusive)
      Description copied from interface: NavigableMap
      Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

      The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

      Specified by:
      tailMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      tailMap in interface NavigableMap<K,​V>
      Parameters:
      fromKey - low endpoint of the keys in the returned map
      inclusive - true if the low endpoint is to be included in the returned view
      Returns:
      a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) 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). Implementations may, but are not required to, throw this exception if fromKey cannot be compared to keys currently in the map.
      NullPointerException - if fromKey is null
      IllegalArgumentException - if this map itself has a restricted range, and fromKey lies outside the bounds of the range

    • subMap

      public ConcurrentNavigableMap<K,​V> subMap​(K fromKey, K toKey)
      Description copied from interface: NavigableMap
      Returns a sorted map over a range of this sorted map with all keys greater than or equal to the specified startKey and less than the specified endKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

      Note: The returned map will not allow an insertion of a key outside the specified range.

      Equivalent to subMap(fromKey, true, toKey, false).

      Specified by:
      subMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      subMap in interface NavigableMap<K,​V>
      Specified by:
      subMap in interface SortedMap<K,​V>
      Parameters:
      fromKey - the low boundary of the range (inclusive).
      toKey - the high boundary of the range (exclusive),
      Returns:
      a sorted map with the key from the specified range.
      Throws:
      ClassCastException - if the class of the start or end key is inappropriate for this sorted map.
      NullPointerException - if fromKey or toKey is null
      IllegalArgumentException - if the start key is greater than the end key, or if this map is itself a sorted map over a range of another sorted map and the specified range is outside of its range.

    • headMap

      public ConcurrentNavigableMap<K,​V> headMap​(K toKey)
      Description copied from interface: NavigableMap
      Returns a sorted map over a range of this sorted map with all keys that are less than the specified endKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

      Note: The returned map will not allow an insertion of a key outside the specified range.

      Equivalent to headMap(toKey, false).

      Specified by:
      headMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      headMap in interface NavigableMap<K,​V>
      Specified by:
      headMap in interface SortedMap<K,​V>
      Parameters:
      toKey - the high boundary of the range specified.
      Returns:
      a sorted map where the keys are less than endKey.
      Throws:
      ClassCastException - if the class of the end key is inappropriate for this sorted map.
      NullPointerException - if toKey is null
      IllegalArgumentException - if this map is itself a sorted map over a range of another map and the specified key is outside of its range.

    • tailMap

      public ConcurrentNavigableMap<K,​V> tailMap​(K fromKey)
      Description copied from interface: NavigableMap
      Returns a sorted map over a range of this sorted map with all keys that are greater than or equal to the specified startKey. Changes to the returned sorted map are reflected in this sorted map and vice versa.

      Note: The returned map will not allow an insertion of a key outside the specified range.

      Equivalent to tailMap(fromKey, true).

      Specified by:
      tailMap in interface ConcurrentNavigableMap<K,​V>
      Specified by:
      tailMap in interface NavigableMap<K,​V>
      Specified by:
      tailMap in interface SortedMap<K,​V>
      Parameters:
      fromKey - the low boundary of the range specified.
      Returns:
      a sorted map where the keys are greater or equal to startKey.
      Throws:
      ClassCastException - if the class of the start key is inappropriate for this sorted map.
      NullPointerException - if fromKey is null
      IllegalArgumentException - if this map itself a sorted map over a range of another map and the specified key is outside of its range.

    • 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 key. 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 the greatest key less than key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • lowerKey

      public K lowerKey​(K key)
      Description copied from interface: NavigableMap
      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 key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified 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 key. 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 with the greatest key less than or equal to key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • floorKey

      public K floorKey​(K key)
      Description copied from interface: NavigableMap
      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 greatest key less than or equal to key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key 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 with the least key greater than or equal to key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • ceilingKey

      public K ceilingKey​(K key)
      Description copied from interface: NavigableMap
      Returns the 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 least key greater than or equal to key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified 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 key. 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 the least key greater than key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified key is null

    • higherKey

      public K higherKey​(K key)
      Description copied from interface: NavigableMap
      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 key, or null if there is no such key
      Throws:
      ClassCastException - if the specified key cannot be compared with the keys currently in the map
      NullPointerException - if the specified 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>

    • 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>

    • 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 this 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 this map is empty