Added in API level 1

TreeMap

open class TreeMap<K : Any!, V : Any!> : AbstractMap<K, V>, Cloneable, NavigableMap<K, V>, Serializable, MutableMap<K, V>

kotlin.Any
↳	java.util.AbstractMap<K, V>
	↳	java.util.TreeMap

A Red-Black tree based NavigableMap implementation. The map is sorted according to the 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.

The methods ceilingEntry, #firstEntry, floorEntry, higherEntry, #lastEntry, lowerEntry, #pollFirstEntry, and #pollLastEntry return Map.Entry instances that represent snapshots of mappings as of the time of the call. They do not support mutation of the underlying map via the optional setValue method.

The #putFirst and #putLast methods of this class throw UnsupportedOperationException. The encounter order of mappings is determined by the comparison method; therefore, explicit positioning is not supported.

This class is a member of the Java Collections Framework.

Summary

Public constructors
`TreeMap()` Constructs a new, empty tree map, using the natural ordering of its keys.
`TreeMap(comparator: Comparator<in K>?)` Constructs a new, empty tree map, ordered according to the given comparator.
`TreeMap(m: MutableMap<out K, out V>)` Constructs a new tree map containing the same mappings as the given map, ordered according to the natural ordering of its keys.
`TreeMap(m: SortedMap<K, out V>)` Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map.

Public methods
open MutableEntry<K, V>?	`ceilingEntry(key: K)`
open K?	`ceilingKey(key: K)`
open Unit	`clear()` Removes all of the mappings from this map.
open Any	`clone()` Returns a shallow copy of this `TreeMap` instance.
open Comparator<in K>?	`comparator()`
open V?	`compute(key: K, remappingFunction: BiFunction<in K, in V?, out V?>)` Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
open V	`computeIfAbsent(key: K, mappingFunction: Function<in K, out V>)` If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
open V?	`computeIfPresent(key: K, remappingFunction: BiFunction<in K, in V, out V?>)` If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
open Boolean	`containsKey(key: K)` Returns `true` if this map contains a mapping for the specified key.
open Boolean	`containsKey(key: K)` Returns `true` if this map contains a mapping for the specified key.
open Boolean	`containsValue(value: V)` Returns `true` if this map maps one or more keys to the specified value.
open Boolean	`containsValue(value: V)` Returns `true` if this map maps one or more keys to the specified value.
open NavigableSet<K>	`descendingKeySet()`
open NavigableMap<K, V>	`descendingMap()`
open MutableEntry<K, V>?	`firstEntry()`
open K	`firstKey()`
open MutableEntry<K, V>?	`floorEntry(key: K)`
open K?	`floorKey(key: K)`
open Unit	`forEach(action: BiConsumer<in K, in V>)`
open V?	`get(key: K)` Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
open V?	`get(key: K)` Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
open SortedMap<K, V>	`headMap(toKey: K)`
open NavigableMap<K, V>	`headMap(toKey: K, inclusive: Boolean)`
open MutableEntry<K, V>?	`higherEntry(key: K)`
open K?	`higherKey(key: K)`
open MutableEntry<K, V>?	`lastEntry()`
open K	`lastKey()`
open MutableEntry<K, V>?	`lowerEntry(key: K)`
open K?	`lowerKey(key: K)`
open V?	`merge(key: K, value: V, remappingFunction: BiFunction<in V, in V, out V?>)` If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
open NavigableSet<K>	`navigableKeySet()`
open MutableEntry<K, V>?	`pollFirstEntry()`
open MutableEntry<K, V>?	`pollLastEntry()`
open V?	`put(key: K, value: V)` Associates the specified value with the specified key in this map.
open Unit	`putAll(from: Map<out K, V>)` Copies all of the mappings from the specified map to this map.
open V?	`putFirst(k: K, v: V)` Throws `UnsupportedOperationException`.
open V?	`putIfAbsent(key: K, value: V)`
open V?	`putLast(k: K, v: V)` Throws `UnsupportedOperationException`.
open V?	`remove(key: K)` Removes the mapping for this key from this TreeMap if present.
open V?	`remove(key: K)` Removes the mapping for this key from this TreeMap if present.
open V?	`replace(key: K, value: V)`
open Boolean	`replace(key: K, oldValue: V, newValue: V)`
open Unit	`replaceAll(function: BiFunction<in K, in V, out V>)`
open NavigableMap<K, V>	`subMap(fromKey: K, fromInclusive: Boolean, toKey: K, toInclusive: Boolean)`
open SortedMap<K, V>	`subMap(fromKey: K, toKey: K)`
open SortedMap<K, V>	`tailMap(fromKey: K)`
open NavigableMap<K, V>	`tailMap(fromKey: K, inclusive: Boolean)`

Inherited functions

From class SortedMap

`Comparator<in 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.
`K`	`firstKey()` Returns the first (lowest) key currently in this map.
`K`	`lastKey()` Returns the last (highest) key currently in this map.
`V?`	`putFirst(k: K, v: V)` Throws `UnsupportedOperationException`. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.
`V?`	`putLast(k: K, v: V)` Throws `UnsupportedOperationException`. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

From class AbstractMap

`Boolean`	`equals(other: Any?)` 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 ensures that the `equals` method works properly across different implementations of the `Map` interface.
`Int`	`hashCode()` Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hash codes of each entry in the map's `entrySet()` view. This ensures that `m1.equals(m2)` implies that `m1.hashCode()==m2.hashCode()` for any two maps `m1` and `m2`, as required by the general contract of `Object.hashCode`.
`Boolean`	`isEmpty()` Returns `true` if this map contains no key-value mappings.
`String`	`toString()` Returns a string representation of this map. The string representation consists of a list of key-value mappings in the order returned by the map's `entrySet` view's iterator, enclosed in braces (`"{}"`). Adjacent mappings are separated by the characters `", "` (comma and space). Each key-value mapping is rendered as the key followed by an equals sign (`"="`) followed by the associated value. Keys and values are converted to strings as by `String.valueOf(Object)`.

From class SequencedMap

`MutableEntry<K, V>!`	`firstEntry()` Returns the first key-value mapping in this map, or `null` if the map is empty.
`MutableEntry<K, V>!`	`lastEntry()` Returns the last key-value mapping in this map, or `null` if the map is empty.
`MutableEntry<K, V>!`	`pollFirstEntry()` Removes and returns the first key-value mapping in this map, or `null` if the map is empty (optional operation).
`MutableEntry<K, V>!`	`pollLastEntry()` Removes and returns the last key-value mapping in this map, or `null` if the map is empty (optional operation).
`SequencedSet<MutableEntry<K, V>!>!`	`sequencedEntrySet()` Returns a `SequencedSet` view of this map's `entrySet`.
`SequencedSet<K>!`	`sequencedKeySet()` Returns a `SequencedSet` view of this map's `keySet`.
`SequencedCollection<V>!`	`sequencedValues()` Returns a `SequencedCollection` view of this map's `values` collection.

From class NavigableMap

NavigableMap<K, V>

reversed()

Returns a reverse-ordered view of this map. The encounter order of mappings in the returned view is the inverse of the encounter order of mappings in this map. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the implementation permits modifications to this view, the modifications "write through" to the underlying map. Changes to the underlying map might or might not be visible in this reversed view, depending upon the implementation.

This method is equivalent to descendingMap.

Properties
open MutableSet<MutableEntry<K, V>>	`entries` Returns a `Set` view of the mappings contained in this map.
open MutableSet<K>	`keys` Returns a `Set` view of the keys contained in this map.
open Int	`size` Returns the number of key-value mappings in this map.
open MutableCollection<V>	`values` Returns a `Collection` view of the values contained in this map.

Inherited properties

From class SortedMap

MutableSet<MutableEntry<K, V>>

entries

Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in ascending key order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. 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.

MutableSet<K>

keys

Returns a Set 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.

MutableCollection<V>

values

Returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. 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.

Public constructors

TreeMap

Added in API level 1

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.

TreeMap

Added in API level 1

TreeMap(comparator: Comparator<in K>?)

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.

Parameters
`comparator`	Comparator<in K>?: the comparator that will be used to order this map. If `null`, the ordering of the keys will be used.

TreeMap

Added in API level 1

TreeMap(m: MutableMap<out K, out V>)

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.

Parameters
`m`	MutableMap<out K, out V>: the map whose mappings are to be placed in this map

Exceptions
`java.lang.ClassCastException`	if the keys in m are not `Comparable`, or are not mutually comparable
`java.lang.NullPointerException`	if the specified map is null

TreeMap

Added in API level 1

TreeMap(m: SortedMap<K, out V>)

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.

Parameters
`m`	SortedMap<K, out V>: the sorted map whose mappings are to be placed in this map, and whose comparator is to be used to sort this map

Exceptions
`java.lang.NullPointerException`	if the specified map is null

Public methods

ceilingEntry

Added in API level 9

open fun ceilingEntry(key: K): MutableEntry<K, V>?

Parameters
`key`	K: the key

Return
`MutableEntry<K, V>?`	an entry with the least key greater than or equal to `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

ceilingKey

Added in API level 9

open fun ceilingKey(key: K): K?

Parameters
`key`	K: the key

Return
`K?`	the least key greater than or equal to `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

clear

Added in API level 1

open fun clear(): Unit

Removes all of the mappings from this map. The map will be empty after this call returns.

Exceptions
`java.lang.UnsupportedOperationException`	if the `clear` operation is not supported by this map

clone

Added in API level 1

open fun clone(): Any

Returns a shallow copy of this TreeMap instance. (The keys and values themselves are not cloned.)

Return
`Any`	a shallow copy of this map

Exceptions
`java.lang.CloneNotSupportedException`	if the object's class does not support the `Cloneable` interface. Subclasses that override the `clone` method can also throw this exception to indicate that an instance cannot be cloned.

comparator

Added in API level 1

open fun comparator(): Comparator<in K>?

Return
`Comparator<in K>?`	the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys

compute

Added in API level 24

open fun compute(
    key: K, 
    remappingFunction: BiFunction<in K, in V?, out V?>
): V?

Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). For example, to either create or append a String msg to a value mapping:

<code>map.compute(key, (k, v) -&gt; (v == null) ? msg : v.concat(msg))</code>

(Method merge() is often simpler to use for such purposes.)

If the remapping function returns null, the mapping is removed (or remains absent if initially absent). If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

The remapping function should not modify this map during computation.

This method will, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation.

Parameters
`key`	K: key with which the specified value is to be associated
`remappingFunction`	BiFunction<in K, in V?, out V?>: the remapping function to compute a value

Return
`V?`	the new value associated with the specified key, or null if none

Exceptions
`java.lang.NullPointerException`	if the specified key is null and this map does not support null keys, or the remappingFunction is null
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.util.ConcurrentModificationException`	if it is detected that the remapping function modified this map

computeIfAbsent

Added in API level 24

open fun computeIfAbsent(
    key: K, 
    mappingFunction: Function<in K, out V>
): V

If the specified key is not already associated with a value (or is mapped to null), attempts to compute its value using the given mapping function and enters it into this map unless null.

If the mapping function returns null, no mapping is recorded. If the mapping function itself throws an (unchecked) exception, the exception is rethrown, and no mapping is recorded. The most common usage is to construct a new object serving as an initial mapped value or memoized result, as in:

<code>map.computeIfAbsent(key, k -&gt; new Value(f(k)));
  </code>

Or to implement a multi-value map, Map<K,Collection<V>>, supporting multiple values per key:

<code>map.computeIfAbsent(key, k -&gt; new HashSet&lt;V&gt;()).add(v);
  </code>

The mapping function should not modify this map during computation.

This method will, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the mapping function modifies this map during computation.

Parameters
`key`	K: key with which the specified value is to be associated
`mappingFunction`	Function<in K, out V>: the mapping function to compute a value

Return
`V`	the current (existing or computed) value associated with the specified key, or null if the computed value is null

Exceptions
`java.lang.NullPointerException`	if the specified key is null and this map does not support null keys, or the mappingFunction is null
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.util.ConcurrentModificationException`	if it is detected that the mapping function modified this map

computeIfPresent

Added in API level 24

open fun computeIfPresent(
    key: K, 
    remappingFunction: BiFunction<in K, in V, out V?>
): V?

If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.

If the remapping function returns null, the mapping is removed. If the remapping function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

The remapping function should not modify this map during computation.

This method will, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation.

Parameters
`key`	K: key with which the specified value is to be associated
`remappingFunction`	BiFunction<in K, in V, out V?>: the remapping function to compute a value

Return
`V?`	the new value associated with the specified key, or null if none

Exceptions
`java.lang.NullPointerException`	if the specified key is null and this map does not support null keys, or the remappingFunction is null
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.util.ConcurrentModificationException`	if it is detected that the remapping function modified this map

containsKey

Added in API level 1

open fun containsKey(key: K): Boolean

Returns true if this map contains a mapping for the specified key.

Parameters
`key`	K: key whose presence in this map is to be tested

Return
`Boolean`	`true` if this map contains a mapping for the specified key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

containsKey

Added in API level 1

open fun containsKey(key: K): Boolean

Returns true if this map contains a mapping for the specified key.

Parameters
`key`	K: key whose presence in this map is to be tested

Return
`Boolean`	`true` if this map contains a mapping for the specified key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

containsValue

Added in API level 1

open fun containsValue(value: V): Boolean

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.

Parameters
`value`	V: value whose presence in this map is to be tested

Return
`Boolean`	`true` if a mapping to `value` exists; `false` otherwise

Exceptions
`java.lang.ClassCastException`	if the value is of an inappropriate type for this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified value is null and this map does not permit null values (java.util.Collection#)

containsValue

Added in API level 1

open fun containsValue(value: V): Boolean

Parameters
`value`	V: value whose presence in this map is to be tested

Return
`Boolean`	`true` if a mapping to `value` exists; `false` otherwise

Exceptions
`java.lang.ClassCastException`	if the value is of an inappropriate type for this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified value is null and this map does not permit null values (java.util.Collection#)

descendingKeySet

Added in API level 9

open fun descendingKeySet(): NavigableSet<K>

Return
`NavigableSet<K>`	a reverse order navigable set view of the keys in this map

descendingMap

Added in API level 9

open fun descendingMap(): NavigableMap<K, V>

Return
`NavigableMap<K, V>`	a reverse order view of this map

firstEntry

Added in API level 9

open fun firstEntry(): MutableEntry<K, V>?

Return
`MutableEntry<K, V>?`	an entry with the least key, or `null` if this map is empty

firstKey

Added in API level 1

open fun firstKey(): K

Return
`K`	the first (lowest) key currently in this map

Exceptions
`java.util.NoSuchElementException`	if this map is empty

floorEntry

Added in API level 9

open fun floorEntry(key: K): MutableEntry<K, V>?

Parameters
`key`	K: the key

Return
`MutableEntry<K, V>?`	an entry with the greatest key less than or equal to `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

floorKey

Added in API level 9

open fun floorKey(key: K): K?

Parameters
`key`	K: the key

Return
`K?`	the greatest key less than or equal to `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

forEach

Added in API level 24

open fun forEach(action: BiConsumer<in K, in V>): Unit

Parameters
`action`	BiConsumer<in K, in V>: The action to be performed for each entry

Exceptions
`java.lang.NullPointerException`	if the specified action is null
`java.util.ConcurrentModificationException`	if an entry is found to be removed during iteration

get

Added in API level 1

open fun get(key: K): V?

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.

Parameters
`key`	K: the key whose associated value is to be returned

Return
`V?`	the value to which the specified key is mapped, or `null` if this map contains no mapping for the key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

get

Added in API level 1

open fun get(key: K): V?

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

Parameters
`key`	K: the key whose associated value is to be returned

Return
`V?`	the value to which the specified key is mapped, or `null` if this map contains no mapping for the key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

headMap

Added in API level 1

open fun headMap(toKey: K): SortedMap<K, V>

Parameters
`toKey`	K: high endpoint (exclusive) of the keys in the returned map

Return
`SortedMap<K, V>`	a view of the portion of this map whose keys are strictly less than `toKey`

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `toKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.IllegalArgumentException`	if this map itself has a restricted range, and `toKey` lies outside the bounds of the range

headMap

Added in API level 9

open fun headMap(
    toKey: K, 
    inclusive: Boolean
): NavigableMap<K, V>

Parameters
`toKey`	K: high endpoint of the keys in the returned map
`inclusive`	Boolean: `true` if the high endpoint is to be included in the returned view

Return
`NavigableMap<K, V>`	a view of the portion of this map whose keys are less than (or equal to, if `inclusive` is true) `toKey`

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `toKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.IllegalArgumentException`	if this map itself has a restricted range, and `toKey` lies outside the bounds of the range

higherEntry

Added in API level 9

open fun higherEntry(key: K): MutableEntry<K, V>?

Parameters
`key`	K: the key

Return
`MutableEntry<K, V>?`	an entry with the least key greater than `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

higherKey

Added in API level 9

open fun higherKey(key: K): K?

Parameters
`key`	K: the key

Return
`K?`	the least key greater than `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

lastEntry

Added in API level 9

open fun lastEntry(): MutableEntry<K, V>?

Return
`MutableEntry<K, V>?`	an entry with the greatest key, or `null` if this map is empty

lastKey

Added in API level 1

open fun lastKey(): K

Return
`K`	the last (highest) key currently in this map

Exceptions
`java.util.NoSuchElementException`	if this map is empty

lowerEntry

Added in API level 9

open fun lowerEntry(key: K): MutableEntry<K, V>?

Parameters
`key`	K: the key

Return
`MutableEntry<K, V>?`	an entry with the greatest key less than `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

lowerKey

Added in API level 9

open fun lowerKey(key: K): K?

Parameters
`key`	K: the key

Return
`K?`	the greatest key less than `key`, or `null` if there is no such key

Exceptions
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

merge

Added in API level 24

open fun merge(
    key: K, 
    value: V, 
    remappingFunction: BiFunction<in V, in V, out V?>
): V?

If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is null. This method may be of use when combining multiple mapped values for a key. For example, to either create or append a String msg to a value mapping:

<code>map.merge(key, msg, String::concat)
  </code>

The remapping function should not modify this map during computation.

This method will, on a best-effort basis, throw a ConcurrentModificationException if it is detected that the remapping function modifies this map during computation.

Parameters
`key`	K: key with which the resulting value is to be associated
`value`	V: the non-null value to be merged with the existing value associated with the key or, if no existing value or a null value is associated with the key, to be associated with the key
`remappingFunction`	BiFunction<in V, in V, out V?>: the remapping function to recompute a value if present

Return
`V?`	the new value associated with the specified key, or null if no value is associated with the key

Exceptions
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified key is null and this map does not support null keys or the value or remappingFunction is null
`java.util.ConcurrentModificationException`	if it is detected that the remapping function modified this map

navigableKeySet

Added in API level 9

open fun navigableKeySet(): NavigableSet<K>

Return
`NavigableSet<K>`	a navigable set view of the keys in this map

pollFirstEntry

Added in API level 9

open fun pollFirstEntry(): MutableEntry<K, V>?

Return
`MutableEntry<K, V>?`	the removed first entry of this map, or `null` if this map is empty

Exceptions
`java.lang.UnsupportedOperationException`	if this collection implementation does not support this operation

pollLastEntry

Added in API level 9

open fun pollLastEntry(): MutableEntry<K, V>?

Return
`MutableEntry<K, V>?`	the removed last entry of this map, or `null` if this map is empty

Exceptions
`java.lang.UnsupportedOperationException`	if this collection implementation does not support this operation

put

Added in API level 1

open fun put(
    key: K, 
    value: V
): V?

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.

Parameters
`key`	K: key with which the specified value is to be associated
`value`	V: value to be associated with the specified key

Return
`V?`	the previous value associated with `key`, or `null` if there was no mapping for `key`. (A `null` return can also indicate that the map previously associated `null` with `key`.)

Exceptions
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map

putAll

Added in API level 1

open fun putAll(from: Map<out K, V>): Unit

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.

Parameters
`m`	mappings to be stored in this map
`map`	mappings to be stored in this map

Exceptions
`java.lang.UnsupportedOperationException`	if the `putAll` operation is not supported by this map
`java.lang.ClassCastException`	if the class of a key or value in the specified map prevents it from being stored in this map
`java.lang.NullPointerException`	if the specified map is null or the specified map contains a null key and this map does not permit null keys
`java.lang.IllegalArgumentException`	if some property of a key or value in the specified map prevents it from being stored in this map

putFirst

Added in API level 35

open fun putFirst(
    k: K, 
    v: V
): V?

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Parameters
`k`	K: the key
`v`	V: the value

Return
`V?`	the value previously associated with k, or null if none

Exceptions
`java.lang.UnsupportedOperationException`	always

putIfAbsent

Added in API level 24

open fun putIfAbsent(
    key: K, 
    value: V
): V?

Parameters
`key`	K: key with which the specified value is to be associated
`value`	V: value to be associated with the specified key

Return
`V?`	the previous value associated with the specified key, or `null` 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.)

Exceptions
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the key or value is of an inappropriate type for this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified key or value is null, and this map does not permit null keys or values (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map (java.util.Collection#)

putLast

Added in API level 35

open fun putLast(
    k: K, 
    v: V
): V?

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Parameters
`k`	K: the key
`v`	V: the value

Return
`V?`	the value previously associated with k, or null if none

Exceptions
`java.lang.UnsupportedOperationException`	always

remove

Added in API level 1

open fun remove(key: K): V?

Removes the mapping for this key from this TreeMap if present.

Parameters
`key`	K: key for which mapping should be removed

Return
`V?`	the previous value associated with `key`, or `null` if there was no mapping for `key`. (A `null` return can also indicate that the map previously associated `null` with `key`.)

Exceptions
`java.lang.UnsupportedOperationException`	if the `remove` operation is not supported by this map
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

remove

Added in API level 1

open fun remove(key: K): V?

Removes the mapping for this key from this TreeMap if present.

Parameters
`key`	K: key for which mapping should be removed

Return
`V?`	the previous value associated with `key`, or `null` if there was no mapping for `key`. (A `null` return can also indicate that the map previously associated `null` with `key`.)

Exceptions
`java.lang.UnsupportedOperationException`	if the `remove` operation is not supported by this map
`java.lang.ClassCastException`	if the specified key cannot be compared with the keys currently in the map
`java.lang.NullPointerException`	if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys

replace

Added in API level 24

open fun replace(
    key: K, 
    value: V
): V?

Parameters
`key`	K: key with which the specified value is associated
`value`	V: value to be associated with the specified key

Return
`V?`	the previous value associated with the specified key, or `null` 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.)

Exceptions
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of the specified key or value prevents it from being stored in this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified key or value is null, and this map does not permit null keys or values
`java.lang.IllegalArgumentException`	if some property of the specified key or value prevents it from being stored in this map

replace

Added in API level 24

open fun replace(
    key: K, 
    oldValue: V, 
    newValue: V
): Boolean

Parameters
`key`	K: key with which the specified value is associated
`oldValue`	V: value expected to be associated with the specified key
`newValue`	V: value to be associated with the specified key

Return
`Boolean`	`true` if the value was replaced

Exceptions
`java.lang.UnsupportedOperationException`	if the `put` operation is not supported by this map (java.util.Collection#)
`java.lang.ClassCastException`	if the class of a specified key or value prevents it from being stored in this map
`java.lang.NullPointerException`	if oldValue is null and this map does not permit null values (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of a specified key or value prevents it from being stored in this map

replaceAll

Added in API level 24

open fun replaceAll(function: BiFunction<in K, in V, out V>): Unit

Parameters
`function`	BiFunction<in K, in V, out V>: the function to apply to each entry

Exceptions
`java.lang.UnsupportedOperationException`	if the `set` operation is not supported by this map's entry set iterator.
`java.lang.ClassCastException`	if the class of a replacement value prevents it from being stored in this map (java.util.Collection#)
`java.lang.NullPointerException`	if the specified function is null, or if a replacement value is null and this map does not permit null values (java.util.Collection#)
`java.lang.IllegalArgumentException`	if some property of a replacement value prevents it from being stored in this map (java.util.Collection#)
`java.util.ConcurrentModificationException`	if an entry is found to be removed during iteration

subMap

Added in API level 9

open fun subMap(
    fromKey: K, 
    fromInclusive: Boolean, 
    toKey: K, 
    toInclusive: Boolean
): NavigableMap<K, V>

Parameters
`fromKey`	K: low endpoint of the keys in the returned map
`fromInclusive`	Boolean: `true` if the low endpoint is to be included in the returned view
`toKey`	K: high endpoint of the keys in the returned map
`toInclusive`	Boolean: `true` if the high endpoint is to be included in the returned view

Return
`NavigableMap<K, V>`	a view of the portion of this map whose keys range from `fromKey` to `toKey`

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `fromKey` or `toKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.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

subMap

Added in API level 1

open fun subMap(
    fromKey: K, 
    toKey: K
): SortedMap<K, V>

Parameters
`fromKey`	K: low endpoint (inclusive) of the keys in the returned map
`toKey`	K: high endpoint (exclusive) of the keys in the returned map

Return
`SortedMap<K, V>`	a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `fromKey` or `toKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.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

tailMap

Added in API level 1

open fun tailMap(fromKey: K): SortedMap<K, V>

Parameters
`fromKey`	K: low endpoint (inclusive) of the keys in the returned map

Return
`SortedMap<K, V>`	a view of the portion of this map whose keys are greater than or equal to `fromKey`

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `fromKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.IllegalArgumentException`	if this map itself has a restricted range, and `fromKey` lies outside the bounds of the range

tailMap

Added in API level 9

open fun tailMap(
    fromKey: K, 
    inclusive: Boolean
): NavigableMap<K, V>

Parameters
`fromKey`	K: low endpoint of the keys in the returned map
`inclusive`	Boolean: `true` if the low endpoint is to be included in the returned view

Return
`NavigableMap<K, V>`	a view of the portion of this map whose keys are greater than (or equal to, if `inclusive` is true) `fromKey`

Exceptions
`java.lang.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.
`java.lang.NullPointerException`	if `fromKey` is null and this map uses natural ordering, or its comparator does not permit null keys
`java.lang.IllegalArgumentException`	if this map itself has a restricted range, and `fromKey` lies outside the bounds of the range

Properties

entries

Added in API level 1

open val entries: MutableSet<MutableEntry<K, V>>

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 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.

Return
`MutableSet<MutableEntry<K, V>>`	a set view of the mappings contained in this map, sorted in ascending key order

keys

Added in API level 1

open val keys: MutableSet<K>

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 java.util.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.

Return
`MutableSet<K>`	a set view of the keys contained in this map, sorted in ascending order

size

Added in API level 1

open val size: Int

Returns the number of key-value mappings in this map.

Return
`Int`	the number of key-value mappings in this map

values

Added in API level 1

open val values: MutableCollection<V>

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.

Return
`MutableCollection<V>`	a collection view of the values contained in this map, sorted in ascending key order