Package Summary Overview Summary

### class:ConcurrentSkipListMap [NONE]
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 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

### constructor:ConcurrentSkipListMap() [NONE]
### ConcurrentSkipListMap public ConcurrentSkipListMap() Constructs a new, empty map, sorted according to the natural ordering of the keys.

### constructor:ConcurrentSkipListMap(java.util.Comparator) [NONE]
### 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.

### constructor:ConcurrentSkipListMap(java.util.Map) [NONE]
### 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

### constructor:ConcurrentSkipListMap(java.util.SortedMap) [NONE]
### 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:clone() [NONE]
### 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`

### method:containsKey(java.lang.Object) [NONE]
### 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

### method:get(java.lang.Object) [NONE]
### 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

### method:remove(java.lang.Object) [NONE]
### 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

### method:containsValue(java.lang.Object) [NONE]
### 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

### method:size() [NONE]
### size public int size() Returns the number of key-value mappings in this map. If the map contains more than `Integer.MAX_VALUE` elements, returns `Integer.MAX_VALUE`. Specified by: `size` in interface `Map<K, V>` Overrides: `size` in class `AbstractMap<K, V>` Returns: the number of key-value mappings in this map

### method:isEmpty() [NONE]
### 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

### method:clear() [NONE]
### 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

### method:keySet() [NONE]
### 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 is `null` if the map's 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

### method:navigableKeySet() [NONE]
### 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

### method:values() [NONE]
### 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

### method:entrySet() [NONE]
### 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>` Returns: a set view of the mappings contained in this map, sorted in ascending key order

### method:descendingMap() [NONE]
### 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

### method:descendingKeySet() [NONE]
### 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

### method:equals(java.lang.Object) [NONE]
- ### 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, associates it with the given value. This is equivalent to, for this `map`:
       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

### method:remove(java.lang.Object,java.lang.Object) [NONE]
### 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, for this `map`:
     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, for this `map`:
       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, for this `map`:
       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

### method:comparator() [NONE]
### 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

### method:firstKey() [NONE]
### 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

### method:lastKey() [NONE]
### 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

### method:firstEntry() [NONE]
### 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

### method:lastEntry() [NONE]
### 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

### method:pollFirstEntry() [NONE]
### 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

### method:pollLastEntry() [NONE]
### 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