Added in API level 1

Hashtable

open class Hashtable<K : Any!, V : Any!> : Dictionary<K, V>, MutableMap<K, V>, Cloneable, Serializable

kotlin.Any
↳	java.util.Dictionary<K, V>
	↳	java.util.Hashtable

Known Direct Subclasses Properties Properties The Properties class represents a persistent set of properties.

Known Indirect Subclasses AuthProvider, Provider AuthProvider Legacy security code; do not use. Provider This class represents a "provider" for the Java Security API, where a provider implements some or all parts of Java Security.

This class implements a hash table, which maps keys to values. Any non-null object can be used as a key or as a value.

To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method and the equals method.

An instance of Hashtable has two parameters that affect its performance: initial capacity and load factor. The capacity is the number of buckets in the hash table, and the initial capacity is simply the capacity at the time the hash table is created. Note that the hash table is open: in the case of a "hash collision", a single bucket stores multiple entries, which must be searched sequentially. The load factor is a measure of how full the hash table is allowed to get before its capacity is automatically increased. The initial capacity and load factor parameters are merely hints to the implementation. The exact details as to when and whether the rehash method is invoked are implementation-dependent.

Generally, the default load factor (.75) offers a good tradeoff between time and space costs. Higher values decrease the space overhead but increase the time cost to look up an entry (which is reflected in most Hashtable operations, including get and put).

The initial capacity controls a tradeoff between wasted space and the need for rehash operations, which are time-consuming. No rehash operations will ever occur if the initial capacity is greater than the maximum number of entries the Hashtable will contain divided by its load factor. However, setting the initial capacity too high can waste space.

If many entries are to be made into a Hashtable, creating it with a sufficiently large capacity may allow the entries to be inserted more efficiently than letting it perform automatic rehashing as needed to grow the table.

This example creates a hashtable of numbers. It uses the names of the numbers as keys:

<code>Hashtable&lt;String, Integer&gt; numbers
      = new Hashtable&lt;String, Integer&gt;();
    numbers.put("one", 1);
    numbers.put("two", 2);
    numbers.put("three", 3);</code>

To retrieve a number, use the following code:

<code>Integer n = numbers.get("two");
    if (n != null) {
      System.out.println("two = " + n);
    }</code>

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 Hashtable 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. The Enumerations returned by Hashtable's keys and elements methods are not fail-fast; if the Hashtable is structurally modified at any time after the enumeration is created then the results of enumerating are undefined.

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.

As of the Java 2 platform v1.2, this class was retrofitted to implement the Map interface, making it a member of the Java Collections Framework. Unlike the new collection implementations, Hashtable is synchronized. If a thread-safe implementation is not needed, it is recommended to use HashMap in place of Hashtable. If a thread-safe highly-concurrent implementation is desired, then it is recommended to use java.util.concurrent.ConcurrentHashMap in place of Hashtable.

Summary

Public constructors
Hashtable(initialCapacity: Int, loadFactor: Float) Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.
Hashtable(initialCapacity: Int) Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).
Hashtable() Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).
Hashtable(t: MutableMap<out K, out V>!) Constructs a new hashtable with the same mappings as the given Map.

Public methods
open Unit	clear() Clears this hashtable so that it contains no keys.
open Any	clone() Creates a shallow copy of this hashtable.
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	contains(value: Any!) Tests if some key maps into the specified value in this hashtable.
open Boolean	containsKey(key: K) Tests if the specified object is a key in this hashtable.
open Boolean	containsValue(value: V) Returns true if this hashtable maps one or more keys to this value.
open Enumeration<V>!	elements() Returns an enumeration of the values in this hashtable.
open Boolean	equals(other: Any?) Compares the specified Object with this Map for equality, as per the definition in the Map interface.
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	getOrDefault(key: K, defaultValue: V)
open Int	hashCode() Returns the hash code value for this Map as per the definition in the Map interface.
open Boolean	isEmpty() Tests if this hashtable maps no keys to values.
open Enumeration<K>!	keys() Returns an enumeration of the keys in this hashtable.
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 V?	put(key: K, value: V) Maps the specified key to the specified value in this hashtable.
open Unit	putAll(from: Map<out K, V>) Copies all of the mappings from the specified map to this hashtable.
open V?	putIfAbsent(key: K, value: V)
open V?	remove(key: K) Removes the key (and its corresponding value) from this hashtable.
open Boolean	remove(key: K, value: V)
open Boolean	replace(key: K, oldValue: V, newValue: V)
open V?	replace(key: K, value: V)
open Unit	replaceAll(function: BiFunction<in K, in V, out V>)
open String	toString() Returns a string representation of this Hashtable object in the form of a set of entries, enclosed in braces and separated by the ASCII characters " , " (comma and space).

Protected methods
open Unit	rehash() Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently.

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 keys in this hashtable.
open MutableCollection<V>	values Returns a Collection view of the values contained in this map.

Public constructors

Hashtable

Added in API level 1

Hashtable(
    initialCapacity: Int, 
    loadFactor: Float)

Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.

Parameters
initialCapacity	Int: the initial capacity of the hashtable.
loadFactor	Float: the load factor of the hashtable.

Exceptions
java.lang.IllegalArgumentException	if the initial capacity is less than zero, or if the load factor is nonpositive.

Hashtable

Added in API level 1

Hashtable(initialCapacity: Int)

Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).

Parameters
initialCapacity	Int: the initial capacity of the hashtable.

Exceptions
java.lang.IllegalArgumentException	if the initial capacity is less than zero.

Hashtable

Added in API level 1

Hashtable()

Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).

Hashtable

Added in API level 1

Hashtable(t: MutableMap<out K, out V>!)

Constructs a new hashtable with the same mappings as the given Map. The hashtable is created with an initial capacity sufficient to hold the mappings in the given Map and a default load factor (0.75).

Parameters
t	MutableMap<out K, out V>!: the map whose mappings are to be placed in this map.

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

Public methods

clear

Added in API level 1

open fun clear(): Unit

Clears this hashtable so that it contains no keys.

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

clone

Added in API level 1

open fun clone(): Any

Creates a shallow copy of this hashtable. All the structure of the hashtable itself is copied, but the keys and values are not cloned. This is a relatively expensive operation.

Return
Any	a clone of the hashtable

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.

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 java.util.ConcurrentModificationException if the remapping function modified 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 (optional)
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map (optional)
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map (optional)
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 java.util.ConcurrentModificationException if the mapping function modified 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 (optional)
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map (optional)
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map (optional)
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 java.util.ConcurrentModificationException if the remapping function modified 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 (optional)
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map (optional)
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map (optional)
java.util.ConcurrentModificationException	if it is detected that the remapping function modified this map

contains

Added in API level 1

open fun contains(value: Any!): Boolean

Tests if some key maps into the specified value in this hashtable. This operation is more expensive than the containsKey method.

Note that this method is identical in functionality to containsValue, (which is part of the Map interface in the collections framework).

Parameters
value	Any!: a value to search for

Return
Boolean	true if and only if some key maps to the value argument in this hashtable as determined by the equals method; false otherwise.

Exceptions
java.lang.NullPointerException	if the value is null

containsKey

Added in API level 1

open fun containsKey(key: K): Boolean

Tests if the specified object is a key in this hashtable.

Parameters
key	K: possible key

Return
Boolean	true if and only if the specified object is a key in this hashtable, as determined by the equals method; false otherwise.

Exceptions
java.lang.ClassCastException	if the key is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if the key is null

See Also

• #contains(Object)

containsValue

Added in API level 1

open fun containsValue(value: V): Boolean

Returns true if this hashtable maps one or more keys to this value.

Note that this method is identical in functionality to contains (which predates the Map interface).

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

Return
Boolean	true if this map maps one or more keys to the specified value

Exceptions
java.lang.ClassCastException	if the value is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if the value is null

elements

Added in API level 1

open fun elements(): Enumeration<V>!

Returns an enumeration of the values in this hashtable. Use the Enumeration methods on the returned object to fetch the elements sequentially. If the hashtable is structurally modified while enumerating over the values then the results of enumerating are undefined.

Return
Enumeration<V>!	an enumeration of the values in this hashtable.

See Also

• java.util.Enumeration
• #keys()
• #values()
• java.util.Map

equals

Added in API level 1

open fun equals(other: Any?): Boolean

Compares the specified Object with this Map for equality, as per the definition in the Map interface.

Parameters
obj	the reference object with which to compare.
o	object to be compared for equality with this hashtable

Return
Boolean	true if the specified Object is equal to this Map

See Also

• java.util.Map#equals(Object)

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.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

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.NullPointerException	if the specified key is null
java.lang.ClassCastException	if the key is of an inappropriate type for this map (optional)

See Also

• #put(Object, Object)

getOrDefault

Added in API level 24

open fun getOrDefault(
    key: K, 
    defaultValue: V
): V

Parameters
key	K: the key whose associated value is to be returned
defaultValue	V: the default mapping of the key

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

Exceptions
java.lang.ClassCastException	if the key is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if the specified key is null and this map does not permit null keys (optional)

hashCode

Added in API level 1

open fun hashCode(): Int

Returns the hash code value for this Map as per the definition in the Map interface.

Return
Int	the hash code value for this map

See Also

• java.util.Map#hashCode()

isEmpty

Added in API level 1

open fun isEmpty(): Boolean

Tests if this hashtable maps no keys to values.

Return
Boolean	true if this hashtable maps no keys to values; false otherwise.

keys

Added in API level 1

open fun keys(): Enumeration<K>!

Returns an enumeration of the keys in this hashtable. Use the Enumeration methods on the returned object to fetch the keys sequentially. If the hashtable is structurally modified while enumerating over the keys then the results of enumerating are undefined.

Return
Enumeration<K>!	an enumeration of the keys in this hashtable.

See Also

• java.util.Enumeration
• #elements()
• #keySet()
• java.util.Map

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>

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 java.util.ConcurrentModificationException if the remapping function modified 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 (optional)
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map (optional)
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map (optional)
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

put

Added in API level 1

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

Maps the specified key to the specified value in this hashtable. Neither the key nor the value can be null.

The value can be retrieved by calling the get method with a key that is equal to the original key.

Parameters
key	K: the hashtable key
value	V: the value

Return
V?	the previous value of the specified key in this hashtable, or null if it did not have one

Exceptions
java.lang.NullPointerException	if the key or value is null
java.lang.UnsupportedOperationException	if the put operation is not supported by this map
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map

See Also

• java.lang.Object#equals(Object)
• #get(Object)

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 hashtable. These mappings will replace any mappings that this hashtable had for any of the keys currently in the specified map.

Parameters
m	mappings to be stored in this map
t	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
java.lang.IllegalArgumentException	if some property of a key or value in the specified map prevents it from being stored in this map

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 (optional)
java.lang.ClassCastException	if the key or value is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if the specified key or value is null, and this map does not permit null keys or values (optional)
java.lang.IllegalArgumentException	if some property of the specified key or value prevents it from being stored in this map (optional)

remove

Added in API level 1

open fun remove(key: K): V?

Removes the key (and its corresponding value) from this hashtable. This method does nothing if the key is not in the hashtable.

Parameters
key	K: the key that needs to be removed

Return
V?	the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping

Exceptions
java.lang.NullPointerException	if the key is null
java.lang.UnsupportedOperationException	if the remove operation is not supported by this map
java.lang.ClassCastException	if the key is of an inappropriate type for this map (optional)

remove

Added in API level 24

open fun remove(
    key: K, 
    value: V
): Boolean

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

Return
Boolean	true if the value was removed

Exceptions
java.lang.UnsupportedOperationException	if the remove operation is not supported by this map (optional)
java.lang.ClassCastException	if the key or value is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if the specified key or value is null, and this map does not permit null keys or values (optional)

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 (optional)
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 (optional)
java.lang.IllegalArgumentException	if some property of a specified key or value prevents it from being stored in this map

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 (optional)
java.lang.ClassCastException	if the class of the specified key or value prevents it from being stored in this map (optional)
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

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 a replacement value is of an inappropriate type for this map (optional)
java.lang.NullPointerException	if function or a replacement value is null, and this map does not permit null keys or values (optional)
java.lang.IllegalArgumentException	if some property of a replacement value prevents it from being stored in this map (optional)
java.util.ConcurrentModificationException	if an entry is found to be removed during iteration

toString

Added in API level 1

open fun toString(): String

Returns a string representation of this Hashtable object in the form of a set of entries, enclosed in braces and separated by the ASCII characters " , " (comma and space). Each entry is rendered as the key, an equals sign =, and the associated element, where the toString method is used to convert the key and element to strings.

Return
String	a string representation of this hashtable

Protected methods

rehash

Added in API level 1

protected open fun rehash(): Unit

Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently. This method is called automatically when the number of keys in the hashtable exceeds this hashtable's capacity and load factor.

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 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

keys

Added in API level 1

open val keys: MutableSet<K>

Returns a Set view of the keys contained in this map. 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

size

Added in API level 1

open val size: Int

Returns the number of keys in this hashtable.

Return
Int	the number of keys in this hashtable.

values

Added in API level 1

open val values: MutableCollection<V>

Returns a Collection view of the values contained in this map. 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