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java.lang.Objectgoodsjpi.IdentityHashtable
This class implements a IdentityHashtable, which maps key object to some
other object.
An instance of IdentityHashtable
has two parameters that
affect its efficiency: its capacity and its load
factor. The load factor should be between 0.0 and 1.0. When
the number of entries in the IdentityHashtable exceeds the product of the
load factor and the current capacity, the capacity is increased by
calling the rehash
method. Larger load factors use
memory more efficiently, at the expense of larger expected time
per lookup.
If many entries are to be made into a IdentityHashtable
,
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.
Constructor Summary | |
IdentityHashtable()
Constructs a new, empty IdentityHashtable with a default capacity and load factor. |
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IdentityHashtable(int initialCapacity)
Constructs a new, empty IdentityHashtable with the specified initial capacity and default load factor. |
|
IdentityHashtable(int initialCapacity,
float loadFactor)
Constructs a new, empty IdentityHashtable with the specified initial capacity and the specified load factor. |
Method Summary | |
void |
clear()
Clears this IdentityHashtable so that it contains no keys. |
boolean |
contains(java.lang.Object value)
Tests if some key maps into the specified value in this IdentityHashtable. |
boolean |
containsKey(java.lang.Object key)
Tests if the specified object is a key in this IdentityHashtable. |
java.lang.Object |
get(java.lang.Object key)
Returns the value to which the specified key is mapped in this IdentityHashtable. |
boolean |
isEmpty()
Tests if this IdentityHashtable maps no keys to values. |
java.lang.Object |
put(java.lang.Object key,
java.lang.Object value)
Maps the specified key to the specified
value in this IdentityHashtable. |
protected void |
rehash()
Rehashes the contents of the IdentityHashtable into a IdentityHashtable with a larger capacity. |
java.lang.Object |
remove(java.lang.Object key)
Removes the key (and its corresponding value) from this IdentityHashtable. |
int |
size()
Returns the number of keys in this IdentityHashtable. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public IdentityHashtable(int initialCapacity, float loadFactor)
initialCapacity
- the initial capacity of the Hashtable.loadFactor
- a number between 0.0 and 1.0.
java.lang.IllegalArgumentException
- if the initial capacity is less
than or equal to zero, or if the load factor is less than
or equal to zero.public IdentityHashtable(int initialCapacity)
initialCapacity
- the initial capacity of the IdentityHashtable.public IdentityHashtable()
Method Detail |
public int size()
public boolean isEmpty()
true
if this Hashtable maps no keys to values;
false
otherwise.public boolean contains(java.lang.Object value)
containsKey
method.
value
- a value to search for.
true
if some key maps to the
value
argument in this IdentityHashtable;
false
otherwise.public boolean containsKey(java.lang.Object key)
key
- possible key.
true
if the specified object is a key in this
IdentityHashtable; false
otherwise.public java.lang.Object get(java.lang.Object key)
key
- a key in the IdentityHashtable.
null
if the key is not mapped to any value in
this IdentityHashtable.protected void rehash()
public java.lang.Object put(java.lang.Object key, java.lang.Object value)
key
to the specified
value
in this IdentityHashtable. 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.
key
- the IdentityHashtable key.value
- the value.
null
if it did not have one.public java.lang.Object remove(java.lang.Object key)
key
- the key that needs to be removed.
null
if the key did not have a mapping.public void clear()
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