Hashtable

java.lang.Object
- java.util.Dictionary<K,V>
- - java.util.Hashtable<K,V>

所有已实现的接口:

Serializable, Cloneable, Map<K,V>

直接已知子类:

Properties
```
public class Hashtable<K,V>
extends Dictionary<K,V>
implements Map<K,V>, Cloneable, Serializable
```
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:
```
   
   Hashtable<String, Integer> numbers
     = new Hashtable<String, Integer>();
   numbers.put("one", 1);
   numbers.put("two", 2);
   numbers.put("three", 3);
```
To retrieve a number, use the following code:
```
   
   Integer n = numbers.get("two");
   if (n != null) {
     System.out.println("two = " + n);
   }
```
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.
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 ConcurrentHashMap in place of Hashtable.
从以下版本开始:

JDK1.0

另请参阅:

Object.equals(java.lang.Object), Object.hashCode(), rehash(), Collection, Map, HashMap, TreeMap, 序列化表格

嵌套类概要
- 从接口继承的嵌套类/接口 java.util.Map
  Map.Entry<K,V>

构造器概要

构造器
构造器	说明
`Hashtable()`	Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).
`Hashtable(int initialCapacity)`	Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).
`Hashtable(int initialCapacity, float loadFactor)`	Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.
`Hashtable(Map<? extends K,? extends V> t)`	Constructs a new hashtable with the same mappings as the given Map.

方法概要

所有方法实例方法具体方法
限定符和类型	方法	说明
`void`	`clear()`	Clears this hashtable so that it contains no keys.
`Object`	`clone()`	Creates a shallow copy of this hashtable.
`V`	`compute(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)`	Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
`V`	`computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)`	If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
`V`	`computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction)`	If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
`boolean`	`contains(Object value)`	Tests if some key maps into the specified value in this hashtable.
`boolean`	`containsKey(Object key)`	Tests if the specified object is a key in this hashtable.
`boolean`	`containsValue(Object value)`	Returns true if this hashtable maps one or more keys to this value.
`Enumeration<V>`	`elements()`	Returns an enumeration of the values in this hashtable.
`Set<Map.Entry<K,V>>`	`entrySet()`	Returns a `Set` view of the mappings contained in this map.
`boolean`	`equals(Object o)`	Compares the specified Object with this Map for equality, as per the definition in the Map interface.
`void`	`forEach(BiConsumer<? super K,? super V> action)`	Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	`get(Object key)`	Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`V`	`getOrDefault(Object key, V defaultValue)`	Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`int`	`hashCode()`	Returns the hash code value for this Map as per the definition in the Map interface.
`boolean`	`isEmpty()`	Tests if this hashtable maps no keys to values.
`Enumeration<K>`	`keys()`	Returns an enumeration of the keys in this hashtable.
`Set<K>`	`keySet()`	Returns a `Set` view of the keys contained in this map.
`V`	`merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)`	If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value.
`V`	`put(K key, V value)`	Maps the specified `key` to the specified `value` in this hashtable.
`void`	`putAll(Map<? extends K,? extends V> t)`	Copies all of the mappings from the specified map to this hashtable.
`V`	`putIfAbsent(K key, V value)`	If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.
`protected void`	`rehash()`	Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently.
`V`	`remove(Object key)`	Removes the key (and its corresponding value) from this hashtable.
`boolean`	`remove(Object key, Object value)`	Removes the entry for the specified key only if it is currently mapped to the specified value.
`V`	`replace(K key, V value)`	Replaces the entry for the specified key only if it is currently mapped to some value.
`boolean`	`replace(K key, V oldValue, V newValue)`	Replaces the entry for the specified key only if currently mapped to the specified value.
`void`	`replaceAll(BiFunction<? super K,? super V,? extends V> function)`	Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.
`int`	`size()`	Returns the number of keys in this hashtable.
`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).
`Collection<V>`	`values()`	Returns a `Collection` view of the values contained in this map.

从类继承的方法 java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

- 构造器详细资料
  - Hashtable
```
public Hashtable(int initialCapacity,
                 float loadFactor)
```
    Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.
    
    参数:
    
    initialCapacity - the initial capacity of the hashtable.
    
    loadFactor - the load factor of the hashtable.
    
    抛出:
    
    IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.
  - Hashtable
```
public Hashtable(int initialCapacity)
```
    Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).
    
    参数:
    
    initialCapacity - the initial capacity of the hashtable.
    
    抛出:
    
    IllegalArgumentException - if the initial capacity is less than zero.
  - Hashtable
```
public Hashtable()
```
    Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).
  - Hashtable
```
public Hashtable(Map<? extends K,? extends V> t)
```
    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).
    
    参数:
    
    t - the map whose mappings are to be placed in this map.
    
    抛出:
    
    NullPointerException - if the specified map is null.
    
    从以下版本开始:
    
    1.2
- 方法详细资料
  - size
```
public int size()
```
    Returns the number of keys in this hashtable.
    
    指定者:
    
    size 在接口中 Map<K,V>
    
    指定者:
    
    size 在类中 Dictionary<K,V>
    
    返回:
    
    the number of keys in this hashtable.
  - isEmpty
```
public boolean isEmpty()
```
    Tests if this hashtable maps no keys to values.
    
    指定者:
    
    isEmpty 在接口中 Map<K,V>
    
    指定者:
    
    isEmpty 在类中 Dictionary<K,V>
    
    返回:
    
    true if this hashtable maps no keys to values; false otherwise.
  - keys
```
public Enumeration<K> keys()
```
    Returns an enumeration of the keys in this hashtable.
    
    指定者:
    
    keys 在类中 Dictionary<K,V>
    
    返回:
    
    an enumeration of the keys in this hashtable.
    
    另请参阅:
    
    Enumeration, elements(), keySet(), Map
  - elements
```
public Enumeration<V> elements()
```
    Returns an enumeration of the values in this hashtable. Use the Enumeration methods on the returned object to fetch the elements sequentially.
    
    指定者:
    
    elements 在类中 Dictionary<K,V>
    
    返回:
    
    an enumeration of the values in this hashtable.
    
    另请参阅:
    
    Enumeration, keys(), values(), Map
  - contains
```
public boolean contains(Object value)
```
    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).
    
    参数:
    
    value - a value to search for
    
    返回:
    
    true if and only if some key maps to the value argument in this hashtable as determined by the equals method; false otherwise.
    
    抛出:
    
    NullPointerException - if the value is null
  - containsValue
```
public boolean containsValue(Object value)
```
    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).
    
    指定者:
    
    containsValue 在接口中 Map<K,V>
    
    参数:
    
    value - value whose presence in this hashtable is to be tested
    
    返回:
    
    true if this map maps one or more keys to the specified value
    
    抛出:
    
    NullPointerException - if the value is null
    
    从以下版本开始:
    
    1.2
  - containsKey
```
public boolean containsKey(Object key)
```
    Tests if the specified object is a key in this hashtable.
    
    指定者:
    
    containsKey 在接口中 Map<K,V>
    
    参数:
    
    key - possible key
    
    返回:
    
    true if and only if the specified object is a key in this hashtable, as determined by the equals method; false otherwise.
    
    抛出:
    
    NullPointerException - if the key is null
    
    另请参阅:
    
    contains(Object)
  - get
```
public V get(Object key)
```
    Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
    More formally, if this map contains a mapping from a key k to a value v such that (key.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)
    
    指定者:
    
    get 在接口中 Map<K,V>
    
    指定者:
    
    get 在类中 Dictionary<K,V>
    
    参数:
    
    key - the key whose associated value is to be returned
    
    返回:
    
    the value to which the specified key is mapped, or null if this map contains no mapping for the key
    
    抛出:
    
    NullPointerException - if the specified key is null
    
    另请参阅:
    
    put(Object, Object)
  - rehash
```
protected void rehash()
```
    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.
  - put
```
public V put(K key,
             V value)
```
    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.
    
    指定者:
    
    put 在接口中 Map<K,V>
    
    指定者:
    
    put 在类中 Dictionary<K,V>
    
    参数:
    
    key - the hashtable key
    
    value - the value
    
    返回:
    
    the previous value of the specified key in this hashtable, or null if it did not have one
    
    抛出:
    
    NullPointerException - if the key or value is null
    
    另请参阅:
    
    Object.equals(Object), get(Object)
  - remove
```
public V remove(Object key)
```
    Removes the key (and its corresponding value) from this hashtable. This method does nothing if the key is not in the hashtable.
    
    指定者:
    
    remove 在接口中 Map<K,V>
    
    指定者:
    
    remove 在类中 Dictionary<K,V>
    
    参数:
    
    key - the key that needs to be removed
    
    返回:
    
    the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping
    
    抛出:
    
    NullPointerException - if the key is null
  - putAll
```
public void putAll(Map<? extends K,? extends V> t)
```
    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.
    
    指定者:
    
    putAll 在接口中 Map<K,V>
    
    参数:
    
    t - mappings to be stored in this map
    
    抛出:
    
    NullPointerException - if the specified map is null
    
    从以下版本开始:
    
    1.2
  - clear
```
public void clear()
```
    Clears this hashtable so that it contains no keys.
    
    指定者:
    
    clear 在接口中 Map<K,V>
  - clone
```
public Object clone()
```
    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.
    
    覆盖:
    
    clone 在类中 Object
    
    返回:
    
    a clone of the hashtable
    
    另请参阅:
    
    Cloneable
  - toString
```
public 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). 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.
    
    覆盖:
    
    toString 在类中 Object
    
    返回:
    
    a string representation of this hashtable
  - keySet
```
public Set<K> keySet()
```
    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.
    
    指定者:
    
    keySet 在接口中 Map<K,V>
    
    返回:
    
    a set view of the keys contained in this map
    
    从以下版本开始:
    
    1.2
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    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.
    
    指定者:
    
    entrySet 在接口中 Map<K,V>
    
    返回:
    
    a set view of the mappings contained in this map
    
    从以下版本开始:
    
    1.2
  - values
```
public Collection<V> values()
```
    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.
    
    指定者:
    
    values 在接口中 Map<K,V>
    
    返回:
    
    a collection view of the values contained in this map
    
    从以下版本开始:
    
    1.2
  - equals
```
public boolean equals(Object o)
```
    Compares the specified Object with this Map for equality, as per the definition in the Map interface.
    
    指定者:
    
    equals 在接口中 Map<K,V>
    
    覆盖:
    
    equals 在类中 Object
    
    参数:
    
    o - object to be compared for equality with this hashtable
    
    返回:
    
    true if the specified Object is equal to this Map
    
    从以下版本开始:
    
    1.2
    
    另请参阅:
    
    Map.equals(Object)
  - hashCode
```
public int hashCode()
```
    Returns the hash code value for this Map as per the definition in the Map interface.
    
    指定者:
    
    hashCode 在接口中 Map<K,V>
    
    覆盖:
    
    hashCode 在类中 Object
    
    返回:
    
    a hash code value for this object.
    
    从以下版本开始:
    
    1.2
    
    另请参阅:
    
    Map.hashCode()
  - getOrDefault
```
public V getOrDefault(Object key,
                      V defaultValue)
```
    从接口复制的说明: Map
    
    Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.
    
    指定者:
    
    getOrDefault 在接口中 Map<K,V>
    
    参数:
    
    key - the key whose associated value is to be returned
    
    defaultValue - the default mapping of the key
    
    返回:
    
    the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key
  - forEach
```
public void forEach(BiConsumer<? super K,? super V> action)
```
    从接口复制的说明: 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.
    
    指定者:
    
    forEach 在接口中 Map<K,V>
    
    参数:
    
    action - The action to be performed for each entry
  - replaceAll
```
public void replaceAll(BiFunction<? super K,? super V,? extends V> function)
```
    从接口复制的说明: 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.
    
    指定者:
    
    replaceAll 在接口中 Map<K,V>
    
    参数:
    
    function - the function to apply to each entry
  - putIfAbsent
```
public V putIfAbsent(K key,
                     V value)
```
    从接口复制的说明: Map
    
    If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value.
    
    指定者:
    
    putIfAbsent 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is to be associated
    
    value - value to be associated with the specified key
    
    返回:
    
    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.)
  - remove
```
public boolean remove(Object key,
                      Object value)
```
    从接口复制的说明: Map
    
    Removes the entry for the specified key only if it is currently mapped to the specified value.
    
    指定者:
    
    remove 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is associated
    
    value - value expected to be associated with the specified key
    
    返回:
    
    true if the value was removed
  - replace
```
public boolean replace(K key,
                       V oldValue,
                       V newValue)
```
    从接口复制的说明: Map
    
    Replaces the entry for the specified key only if currently mapped to the specified value.
    
    指定者:
    
    replace 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is associated
    
    oldValue - value expected to be associated with the specified key
    
    newValue - value to be associated with the specified key
    
    返回:
    
    true if the value was replaced
  - replace
```
public V replace(K key,
                 V value)
```
    从接口复制的说明: Map
    
    Replaces the entry for the specified key only if it is currently mapped to some value.
    
    指定者:
    
    replace 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is associated
    
    value - value to be associated with the specified key
    
    返回:
    
    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.)
  - computeIfAbsent
```
public V computeIfAbsent(K key,
                         Function<? super K,? extends V> mappingFunction)
```
    从接口复制的说明: Map
    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 function returns null no mapping is recorded. If the 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:
```
 
 map.computeIfAbsent(key, k -> new Value(f(k)));
 
```
    Or to implement a multi-value map, Map<K,Collection<V>>, supporting multiple values per key:
```
 
 map.computeIfAbsent(key, k -> new HashSet<V>()).add(v);
 
```
    指定者:
    
    computeIfAbsent 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is to be associated
    
    mappingFunction - the function to compute a value
    
    返回:
    
    the current (existing or computed) value associated with the specified key, or null if the computed value is null
  - computeIfPresent
```
public V computeIfPresent(K key,
                          BiFunction<? super K,? super V,? extends V> remappingFunction)
```
    从接口复制的说明: Map
    
    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 function returns null, the mapping is removed. If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.
    
    指定者:
    
    computeIfPresent 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is to be associated
    
    remappingFunction - the function to compute a value
    
    返回:
    
    the new value associated with the specified key, or null if none
  - compute
```
public V compute(K key,
                 BiFunction<? super K,? super V,? extends V> remappingFunction)
```
    从接口复制的说明: Map
    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:
```
 
 map.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))
```
    (Method merge() is often simpler to use for such purposes.)
    If the function returns null, the mapping is removed (or remains absent if initially absent). If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.
    指定者:
    
    compute 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the specified value is to be associated
    
    remappingFunction - the function to compute a value
    
    返回:
    
    the new value associated with the specified key, or null if none
  - merge
```
public V merge(K key,
               V value,
               BiFunction<? super V,? super V,? extends V> remappingFunction)
```
    从接口复制的说明: Map
    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:
```
 
 map.merge(key, msg, String::concat)
 
```
    If the function returns null the mapping is removed. If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.
    指定者:
    
    merge 在接口中 Map<K,V>
    
    参数:
    
    key - key with which the resulting value is to be associated
    
    value - 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 - the function to recompute a value if present
    
    返回:
    
    the new value associated with the specified key, or null if no value is associated with the key

类 Hashtable<K,V>

嵌套类概要

从接口继承的嵌套类/接口 java.util.Map

构造器概要

方法概要

从类继承的方法 java.lang.Object

构造器详细资料

Hashtable

Hashtable

Hashtable

Hashtable

方法详细资料

size

isEmpty

keys

elements

contains

containsValue

containsKey

get

rehash

put

remove

putAll

clear

clone

toString

keySet

entrySet

values

equals

hashCode

getOrDefault

forEach

replaceAll

putIfAbsent

remove

replace

replace

computeIfAbsent

computeIfPresent

compute

merge