Java compact1, compact2, compact3 java.util.concurrent Class ConcurrentSkipListMap<K,V>（JDK8）

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Java™ Platform
Standard Ed. 8

All Classes

Summary:
Nested |
Field |
Constr |
Method

Detail:
Field |
Constr |
Method

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 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

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 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

All Methods Instance Methods Concrete Methods
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.

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 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.
    
    Specified by:
    
    clear in interface Map<K,V>
    
    Overrides:
    
    clear in class AbstractMap<K,V>
  - 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

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Java compact1, compact2, compact3 java.util.concurrent Class ConcurrentSkipListMap<K,V>（JDK8）

Class ConcurrentSkipListMap<K,V>

Nested Class Summary

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

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

Constructor Summary

Method Summary

Methods inherited from class java.util.AbstractMap

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Constructor Detail

ConcurrentSkipListMap

ConcurrentSkipListMap

ConcurrentSkipListMap

ConcurrentSkipListMap

Method Detail

clone

containsKey

get

getOrDefault

put

remove

containsValue

size

isEmpty

clear

computeIfAbsent

computeIfPresent

compute

merge

keySet

navigableKeySet

values

entrySet

descendingMap

descendingKeySet

equals

putIfAbsent

remove

replace

replace

comparator

firstKey

lastKey

subMap

headMap

tailMap

subMap

headMap

tailMap

lowerEntry

lowerKey

floorEntry

floorKey

ceilingEntry

ceilingKey

higherEntry

higherKey

firstEntry

lastEntry

pollFirstEntry

pollLastEntry

forEach

replaceAll