java.util.concurrent

Class 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 and spliterators are weakly consistent.

    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.

    This class is a member of the Java Collections Framework.

    Since:
    1.6
    See Also:
    Serialized Form

    • 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 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 order the keys in this map, or null if this map uses the natural ordering of its keys.
      V compute(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)
      Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).
      V computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)
      If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map unless null.
      V computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)
      If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value.
      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 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 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.
      void forEach(BiConsumer<? super K,? super V> action)
      Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
      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.
      V getOrDefault(Object key, V defaultValue)
      Returns the value to which the specified key is mapped, or the given defaultValue if this map contains no mapping for the key.
      ConcurrentNavigableMap<K,V> headMap(K toKey)
      Returns a view of the portion of this map whose keys are strictly less than toKey.
      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 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 key.
      K lowerKey(K key)
      Returns the greatest key strictly less than the given key, or null if there is no such key.
      V merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)
      If the specified key is not already associated with a value, associates it with the given value.
      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.
      void replaceAll(BiFunction<? super K,? super V,? extends V> function)
      Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
      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 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.
      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.

    • Constructor Detail

      • 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 Detail

      • 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
        See Also:
        Cloneable

      • 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 whose associated value is to be returned
        Returns:
        the value to which the specified key is mapped, or null if this map contains 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

      • getOrDefault

        public V getOrDefault(Object key,
                      V defaultValue)
        Returns the value to which the specified key is mapped, or the given defaultValue if this map contains no mapping for the key.
        Specified by:
        getOrDefault in interface  ConcurrentMap<K,V>
        Specified by:
        getOrDefault in interface  Map<K,V>
        Parameters:
        key - the key
        defaultValue - the value to return if this map contains no mapping for the given key
        Returns:
        the mapping for the key, if present; else the defaultValue
        Throws:
        NullPointerException - if the specified key is null
        Since:
        1.8

      • 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

      • clear

        public void clear()
        Removes all of the mappings from this map.

      • computeIfAbsent

        public V computeIfAbsent(K key,
                         Function<? super K,? extends V> mappingFunction)
        If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this map unless null. The function is NOT guaranteed to be applied once atomically only if the value is not present.
        Specified by:
        computeIfAbsent in interface  ConcurrentMap<K,V>
        Specified by:
        computeIfAbsent in interface  Map<K,V>
        Parameters:
        key - key with which the specified value is to be associated
        mappingFunction - the function to compute a value
        Returns:
        the current (existing or computed) value associated with the specified key, or null if the computed value is null
        Throws:
        NullPointerException - if the specified key is null or the mappingFunction is null
        Since:
        1.8

      • computeIfPresent

        public V computeIfPresent(K key,
                          BiFunction<? super K,? super V,? extends V> remappingFunction)
        If the value for the specified key is present, attempts to compute a new mapping given the key and its current mapped value. The function is NOT guaranteed to be applied once atomically.
        Specified by:
        computeIfPresent in interface  ConcurrentMap<K,V>
        Specified by:
        computeIfPresent in interface  Map<K,V>
        Parameters:
        key - key with which a value may be associated
        remappingFunction - the function to compute a value
        Returns:
        the new value associated with the specified key, or null if none
        Throws:
        NullPointerException - if the specified key is null or the remappingFunction is null
        Since:
        1.8

      • compute

        public V compute(K key,
                 BiFunction<? super K,? super V,? extends V> remappingFunction)
        Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). The function is NOT guaranteed to be applied once atomically.
        Specified by:
        compute in interface  ConcurrentMap<K,V>
        Specified by:
        compute in interface  Map<K,V>
        Parameters:
        key - key with which the specified value is to be associated
        remappingFunction - the function to compute a value
        Returns:
        the new value associated with the specified key, or null if none
        Throws:
        NullPointerException - if the specified key is null or the remappingFunction is null
        Since:
        1.8

      • merge

        public V merge(K key,
               V value,
               BiFunction<? super V,? super V,? extends V> remappingFunction)
        If the specified key is not already associated with a value, associates it with the given value. Otherwise, replaces the value with the results of the given remapping function, or removes if null. The function is NOT guaranteed to be applied once atomically.
        Specified by:
        merge in interface  ConcurrentMap<K,V>
        Specified by:
        merge in interface  Map<K,V>
        Parameters:
        key - key with which the specified value is to be associated
        value - the value to use if absent
        remappingFunction - the function to recompute a value if present
        Returns:
        the new value associated with the specified key, or null if none
        Throws:
        NullPointerException - if the specified key or value is null or the remappingFunction is null
        Since:
        1.8

      • 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's spliterator additionally reports Spliterator.CONCURRENT, Spliterator.NONNULL, Spliterator.SORTED and Spliterator.ORDERED, with an encounter order that is ascending key order. The spliterator's comparator (see Spliterator.getComparator()) is null if the map's comparator (see comparator()) is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the map's comparator.

        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 iterators and spliterators are weakly consistent.

        This method is equivalent to method navigableKeySet.

        Specified by:
        keySet in interface  ConcurrentNavigableMap<K,V>
        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 navigable set view of the keys in this map

      • navigableKeySet

        public NavigableSet<K> navigableKeySet()
        Description copied from interface: ConcurrentNavigableMap
        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 iterators and spliterators are weakly consistent.

        Specified by:
        navigableKeySet in interface  ConcurrentNavigableMap<K,V>
        Specified by:
        navigableKeySet in interface  NavigableMap<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 collections's spliterator additionally reports Spliterator.CONCURRENT, Spliterator.NONNULL and Spliterator.ORDERED, with an encounter order that is 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 iterators and spliterators are weakly consistent.

        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 Set view of the mappings contained in this map.

        The set's iterator returns the entries in ascending key order. The set's spliterator additionally reports Spliterator.CONCURRENT, Spliterator.NONNULL, Spliterator.SORTED and Spliterator.ORDERED, with an encounter order that is 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 iterators and spliterators are weakly consistent.

        The Map.Entry elements traversed by the iterator or spliterator 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 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 iterators and spliterators are weakly consistent.

        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(), HashMap

      • 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:
        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) && Objects.equals(map.get(key), 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 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) && Objects.equals(map.get(key), 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 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>
        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:
        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 order the keys in this map, or null if this map uses the natural ordering of its keys.
        Specified by:
        comparator in interface  SortedMap<K,V>
        Returns:
        the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys

      • firstKey

        public K firstKey()
        Description copied from interface: SortedMap
        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 - if this map is empty

      • lastKey

        public K lastKey()
        Description copied from interface: SortedMap
        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 - if this 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 fromInclusive and toInclusive 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 view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) 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.

        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 - low endpoint (inclusive) of the keys in the returned map
        toKey - high endpoint (exclusive) of the keys in the returned map
        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). 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)
        Description copied from interface: NavigableMap
        Returns a view of the portion of this map whose keys are strictly less than 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.

        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 - high endpoint (exclusive) of the keys in the returned map
        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). 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)
        Description copied from interface: NavigableMap
        Returns a view of the portion of this map whose keys are greater than or equal to 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.

        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 - low endpoint (inclusive) of the keys in the returned map
        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). 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

      • 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>
        Returns:
        an entry with the least key, or null if this 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 the greatest key, or null if this 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 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

      • forEach

        public void forEach(BiConsumer<? super K,? super V> action)
        Description copied from interface: ConcurrentMap
        Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.
        Specified by:
        forEach in interface  ConcurrentMap<K,V>
        Specified by:
        forEach in interface  Map<K,V>
        Parameters:
        action - The action to be performed for each entry

      • replaceAll

        public void replaceAll(BiFunction<? super K,? super V,? extends V> function)
        Description copied from interface: ConcurrentMap
        Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. Exceptions thrown by the function are relayed to the caller.
        Specified by:
        replaceAll in interface  ConcurrentMap<K,V>
        Specified by:
        replaceAll in interface  Map<K,V>
        Parameters:
        function - the function to apply to each entry