K - the type of keys maintained by this mapV - the type of mapped valuespublic class TreeMap<K,V> extends AbstractMap<K,V> implements NavigableMap<K,V>, Cloneable, Serializable
A Red-Black tree based NavigableMap 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 implementation provides guaranteed log(n) time cost for the containsKey, get, put and remove operations. Algorithms are adaptations of those in Cormen, Leiserson, and Rivest's Introduction to Algorithms.
Note that the ordering maintained by a tree map, like any sorted map, and whether or not an explicit comparator is provided, must be consistent with equals if this sorted map is to correctly implement the Map interface. (See Comparable or Comparator for a precise definition of consistent with equals.) This is so because the Map interface is defined in terms of the equals operation, but a sorted map performs all key comparisons using its compareTo (or compare) method, so two keys that are deemed equal by this method are, from the standpoint of the sorted map, equal. The behavior of a sorted map is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.
Note that this implementation is not synchronized. If multiple threads access a map concurrently, and at least one of the threads modifies the map structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more mappings; merely changing the value associated with an existing key is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the map. If no such object exists, the map should be "wrapped" using the Collections.synchronizedSortedMap method. This is best done at creation time, to prevent accidental unsynchronized access to the map:
SortedMap m = Collections.synchronizedSortedMap(new TreeMap(...));
The iterators returned by the iterator method of the collections returned by all of this class's "collection view methods" are fail-fast: if the map is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.
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.)
This class is a member of the Java Collections Framework.
Map, HashMap, Hashtable, Comparable, Comparator, Collection, Serialized FormAbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V> public TreeMap()
Constructs a new, empty tree map, using the natural ordering of its keys. All keys inserted into the map must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a ClassCastException for any keys k1 and k2 in the map. If the user attempts to put a key into the map that violates this constraint (for example, the user attempts to put a string key into a map whose keys are integers), the put(Object key, Object value) call will throw a ClassCastException.
public TreeMap(Comparator<? super K> comparator)
Constructs a new, empty tree map, ordered according to the given comparator. All keys inserted into the map must be mutually comparable by the given comparator: comparator.compare(k1,
k2) must not throw a ClassCastException for any keys k1 and k2 in the map. If the user attempts to put a key into the map that violates this constraint, the put(Object
key, Object value) call will throw a ClassCastException.
comparator - the comparator that will be used to order this map. If null, the natural ordering of the keys will be used.public TreeMap(Map<? extends K,? extends V> m)
Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys. All keys inserted into the new map must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a ClassCastException for any keys k1 and k2 in the map. This method runs in n*log(n) time.
m - the map whose mappings are to be placed in this mapClassCastException - if the keys in m are not Comparable, or are not mutually comparableNullPointerException - if the specified map is nullpublic TreeMap(SortedMap<K,? extends V> m)
Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. This method runs in linear time.
m - the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this mapNullPointerException - if the specified map is nullpublic int size()
Returns the number of key-value mappings in this map.
size in interface Map<K,V>
size in class AbstractMap<K,V>
public boolean containsKey(Object key)
Returns true if this map contains a mapping for the specified key.
containsKey in interface Map<K,V>
containsKey in class AbstractMap<K,V>
key - key whose presence in this map is to be testedtrue if this map contains a mapping for the specified keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic boolean containsValue(Object value)
Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)). This operation will probably require time linear in the map size for most implementations.
containsValue in interface Map<K,V>
containsValue in class AbstractMap<K,V>
value - value whose presence in this map is to be testedtrue if a mapping to value exists; false otherwisepublic 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.)
A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.
get in interface Map<K,V>
get in class AbstractMap<K,V>
key - the key whose associated value is to be returnednull if this map contains no mapping for the keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic 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.
comparator in interface SortedMap<K,V>
null if this map uses the natural ordering of its keyspublic K firstKey()
Description copied from interface: SortedMap
Returns the first (lowest) key currently in this map.
firstKey in interface SortedMap<K,V>
NoSuchElementException - if this map is emptypublic K lastKey()
Description copied from interface: SortedMap
Returns the last (highest) key currently in this map.
lastKey in interface SortedMap<K,V>
NoSuchElementException - if this map is emptypublic void putAll(Map<? extends K,? extends V> map)
Copies all of the mappings from the specified map to this map. These mappings replace any mappings that this map had for any of the keys currently in the specified map.
putAll in interface Map<K,V>
putAll in class AbstractMap<K,V>
map - mappings to be stored in this mapClassCastException - if the class of a key or value in the specified map prevents it from being stored in this mapNullPointerException - if the specified map is null or the specified map contains a null key and this map does not permit null keyspublic 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.
put in interface Map<K,V>
put in class AbstractMap<K,V>
key - key with which the specified value is to be associatedvalue - value to be associated with the specified keykey, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)ClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic V remove(Object key)
Removes the mapping for this key from this TreeMap if present.
remove in interface Map<K,V>
remove in class AbstractMap<K,V>
key - key for which mapping should be removedkey, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)ClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic void clear()
Removes all of the mappings from this map. The map will be empty after this call returns.
public Object clone()
Returns a shallow copy of this TreeMap instance. (The keys and values themselves are not cloned.)
clone in class AbstractMap<K,V>
Cloneablepublic Map.Entry<K,V> firstEntry()
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the least key in this map, or null if the map is empty.
firstEntry in interface NavigableMap<K,V>
null if this map is emptypublic Map.Entry<K,V> lastEntry()
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
lastEntry in interface NavigableMap<K,V>
null if this map is emptypublic Map.Entry<K,V> pollFirstEntry()
Description copied from interface: NavigableMap
Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.
pollFirstEntry in interface NavigableMap<K,V>
null if this map is emptypublic Map.Entry<K,V> pollLastEntry()
Description copied from interface: NavigableMap
Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.
pollLastEntry in interface NavigableMap<K,V>
null if this map is emptypublic Map.Entry<K,V> lowerEntry(K key)
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.
lowerEntry in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic 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.
lowerKey in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic Map.Entry<K,V> floorEntry(K key)
Description copied from interface: NavigableMap
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.
floorEntry in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic 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.
floorKey in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic Map.Entry<K,V> ceilingEntry(K key)
Description copied from interface: NavigableMap
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 key.
ceilingEntry in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic 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.
ceilingKey in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic Map.Entry<K,V> higherEntry(K key)
Description copied from interface: NavigableMap
Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.
higherEntry in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic 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.
higherKey in interface NavigableMap<K,V>
key - the keykey, or null if there is no such keyClassCastException - if the specified key cannot be compared with the keys currently in the mapNullPointerException - if the specified key is null and this map uses natural ordering, or its comparator does not permit null keyspublic Set<K> keySet()
Returns a Set view of the keys contained in this map.
The set's iterator returns the keys in ascending order. The set's spliterator is late-binding, fail-fast, and additionally reports 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 tree map's comparator (see comparator()) is null. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the tree map's comparator.
The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. 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.
keySet in interface Map<K,V>
keySet in interface SortedMap<K,V>
keySet in class AbstractMap<K,V>
public NavigableSet<K> navigableKeySet()
Description copied from interface: NavigableMap
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. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. 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.
navigableKeySet in interface NavigableMap<K,V>
public NavigableSet<K> descendingKeySet()
Description copied from interface: NavigableMap
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. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. 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.
descendingKeySet in interface NavigableMap<K,V>
public Collection<V> values()
Returns a Collection view of the values contained in this map.
The collection's iterator returns the values in ascending order of the corresponding keys. The collection's spliterator is late-binding, fail-fast, and additionally reports 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. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. 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.
values in interface Map<K,V>
values in interface SortedMap<K,V>
values in class AbstractMap<K,V>
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 sets's spliterator is late-binding, fail-fast, and additionally reports 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. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. 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.
entrySet in interface Map<K,V>
entrySet in interface SortedMap<K,V>
entrySet in class AbstractMap<K,V>
public NavigableMap<K,V> descendingMap()
Description copied from interface: NavigableMap
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. If either map is modified while an iteration over a collection view of either map is in progress (except through the iterator's own remove operation), the results of the iteration are undefined.
The returned map has an ordering equivalent to Collections.reverseOrder(comparator())m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.
descendingMap in interface NavigableMap<K,V>
public NavigableMap<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.
subMap in interface NavigableMap<K,V>
fromKey - low endpoint of the keys in the returned mapfromInclusive - true if the low endpoint is to be included in the returned viewtoKey - high endpoint of the keys in the returned maptoInclusive - true if the high endpoint is to be included in the returned viewfromKey to toKey
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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - 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 rangepublic NavigableMap<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.
headMap in interface NavigableMap<K,V>
toKey - high endpoint of the keys in the returned mapinclusive - true if the high endpoint is to be included in the returned viewinclusive is true) toKey
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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - if this map itself has a restricted range, and toKey lies outside the bounds of the rangepublic NavigableMap<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.
tailMap in interface NavigableMap<K,V>
fromKey - low endpoint of the keys in the returned mapinclusive - true if the low endpoint is to be included in the returned viewinclusive is true) fromKey
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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - if this map itself has a restricted range, and fromKey lies outside the bounds of the rangepublic SortedMap<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).
subMap in interface NavigableMap<K,V>
subMap in interface SortedMap<K,V>
fromKey - low endpoint (inclusive) of the keys in the returned maptoKey - high endpoint (exclusive) of the keys in the returned mapfromKey, inclusive, to toKey, exclusiveClassCastException - 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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - 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 rangepublic SortedMap<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).
headMap in interface NavigableMap<K,V>
headMap in interface SortedMap<K,V>
toKey - high endpoint (exclusive) of the keys in the returned maptoKey
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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - if this map itself has a restricted range, and toKey lies outside the bounds of the rangepublic SortedMap<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).
tailMap in interface NavigableMap<K,V>
tailMap in interface SortedMap<K,V>
fromKey - low endpoint (inclusive) of the keys in the returned mapfromKey
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 and this map uses natural ordering, or its comparator does not permit null keysIllegalArgumentException - if this map itself has a restricted range, and fromKey lies outside the bounds of the rangepublic boolean replace(K key,
V oldValue,
V newValue) Description copied from interface: Map
Replaces the entry for the specified key only if currently mapped to the specified value.
replace in interface Map<K,V>
key - key with which the specified value is associatedoldValue - value expected to be associated with the specified keynewValue - value to be associated with the specified keytrue if the value was replacedpublic V replace(K key,
V value) Description copied from interface: Map
Replaces the entry for the specified key only if it is currently mapped to some value.
replace in interface Map<K,V>
key - key with which the specified value is associatedvalue - value to be associated with the specified keynull if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the key, if the implementation supports null values.)public void forEach(BiConsumer<? super K,? super V> action)
Description copied from interface: Map
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.
forEach in interface Map<K,V>
action - The action to be performed for each entrypublic void replaceAll(BiFunction<? super K,? super V,? extends V> function)
Description copied from interface: Map
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.
replaceAll in interface Map<K,V>
function - the function to apply to each entry
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