Hashtable (JanosRuntime JavaDOC)

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

Type Parameters:

K - Type used for Keys

V - Type used for Values

All Implemented Interfaces:

Cloneable

Direct Known Subclasses:

Properties
```
public class Hashtable<K,V>
extends Dictionary<K,V>
implements Cloneable
```
This class implements a hash table, which maps keys to values.

Constructor Summary

Constructors
Constructor and Description
`Hashtable()` Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).
`Hashtable(int initcap)` Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).
`Hashtable(int initcap, float loadfact)` Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Clears this hashtable so that it contains no keys.
`Hashtable<K,V>`	`clone()` Creates a new object of the same class as this object.
`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.
`Enumeration<V>`	`elements()` Returns an enumeration of the values in this hashtable.
`V`	`get(K key)` Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`boolean`	`isEmpty()` Tests if this hashtable maps no keys to values.
`Enumeration<K>`	`keys()` Returns an enumeration of the keys in this hashtable.
`V`	`put(K key, V value)` Maps the specified `key` to the specified `value` in this hashtable.
`protected void`	`rehash()` Increases the capacity of and internally reorganizes this hashtable, in order to accommodate and access its entries more efficiently.
`V`	`remove(K key)` Removes the key (and its corresponding value) from this hashtable.
`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).

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Hashtable
```
public Hashtable()
```
    Constructs a new, empty hashtable with a default initial capacity (11) and load factor (0.75).
  - Hashtable
```
public Hashtable(int initcap)
```
    Constructs a new, empty hashtable with the specified initial capacity and default load factor (0.75).
    
    Parameters:
    
    initcap - the initial capacity of the hashtable.
  - Hashtable
```
public Hashtable(int initcap,
                 float loadfact)
```
    Constructs a new, empty hashtable with the specified initial capacity and the specified load factor.
    
    Parameters:
    
    initcap - the initial capacity of the hashtable.
    
    loadfact - the load factor of the hashtable.
    
    Throws:
    
    IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.
- Method Detail
  - clear
```
public void clear()
```
    Clears this hashtable so that it contains no keys.
  - clone
```
public Hashtable<K,V> clone()
```
    Description copied from class: Object
    
    Creates a new object of the same class as this object. It then initializes each of the new object's fields by assigning it the same value as the corresponding field in this object. No constructor is called.
    The clone method of class Object will only clone an object whose class indicates that it is willing for its instances to be cloned. A class indicates that its instances can be cloned by declaring that it implements the Cloneable interface.
    
    Overrides:
    
    clone in class Object
    
    Returns:
    
    a clone of this instance.
    
    See Also:
    
    Cloneable
  - contains
```
public boolean contains(Object value)
```
    Tests if some key maps into the specified value in this hashtable.
    
    Parameters:
    
    value - a value to search for
    
    Returns:
    
    true if and only if some key maps to the value argument in this hashtable as determined by the equals method; false otherwise.
    
    Throws:
    
    NullPointerException - if the value is null
  - containsKey
```
public boolean containsKey(Object key)
```
    Tests if the specified object is a key in this hashtable.
    
    Parameters:
    
    key - possible key
    
    Returns:
    
    true if and only if the specified object is a key in this hashtable, as determined by the equals method; false otherwise.
  - elements
```
public Enumeration<V> elements()
```
    Returns an enumeration of the values in this hashtable.
    
    Specified by:
    
    elements in class Dictionary<K,V>
    
    Returns:
    
    an enumeration of the values in this hashtable.
  - get
```
public V get(K key)
```
    Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
    
    Specified by:
    
    get in class Dictionary<K,V>
    
    Parameters:
    
    key - the key whose associated value is to be returned
    
    Returns:
    
    the value to which the specified key is mapped, or null if this map contains no mapping for the key
    
    Throws:
    
    NullPointerException - if the specified key is null
    
    See Also:
    
    put(Object, Object)
  - isEmpty
```
public boolean isEmpty()
```
    Tests if this hashtable maps no keys to values.
    
    Specified by:
    
    isEmpty in class Dictionary<K,V>
    
    Returns:
    
    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.
    
    Specified by:
    
    keys in class Dictionary<K,V>
    
    Returns:
    
    an enumeration of the keys
  - 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.
    
    Specified by:
    
    put in class Dictionary<K,V>
    
    Parameters:
    
    key - the hashtable key
    
    value - the value
    
    Returns:
    
    the previous value of the specified key in this hashtable, or null if it did not have one
    
    Throws:
    
    NullPointerException - if the key or value is null
  - 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.
  - remove
```
public V remove(K key)
```
    Removes the key (and its corresponding value) from this hashtable. This method does nothing if the key is not in the hashtable.
    
    Specified by:
    
    remove in class Dictionary<K,V>
    
    Parameters:
    
    key - the key that needs to be removed
    
    Returns:
    
    the value to which the key had been mapped in this hashtable, or null if the key did not have a mapping
    
    Throws:
    
    NullPointerException - if the key is null
  - size
```
public int size()
```
    Returns the number of keys in this hashtable.
    
    Specified by:
    
    size in class Dictionary<K,V>
    
    Returns:
    
    the number of keys in this hashtable.
  - 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.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    a string representation of this hashtable

Class Hashtable<K,V>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Hashtable

Hashtable

Hashtable

Method Detail

clear

clone

contains

containsKey

elements

get

isEmpty

keys

put

rehash

remove

size

toString