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Oracle Security Developer Tools Crypto FIPS Java API Reference 11g (11.1.1) E10696-02 |
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java.lang.Object
java.util.Dictionary
oracle.security.crypto.util.UnsyncHashtable
public final class UnsyncHashtable
This class implements a hashtable, 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 UnsyncHashtable
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 hashtable 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 UnsyncHashtable
, 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:
UnsyncHashtable numbers = new UnsyncHashtable(); numbers.put("one", new Integer(1)); numbers.put("two", new Integer(2)); numbers.put("three", new Integer(3));
To retrieve a number, use the following code:
Integer n = (Integer)numbers.get("two"); if (n != null) { System.out.println("two = " + n); }
Constructor Summary | |
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UnsyncHashtable() Constructs a new, empty hashtable with a default capacity and load factor. |
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UnsyncHashtable(int initialCapacity) Constructs a new, empty hashtable with the specified initial capacity and default load factor. |
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UnsyncHashtable(int initialCapacity, float loadFactor) Constructs a new, empty hashtable with the specified initial capacity and the specified load factor. |
Method Summary | |
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void |
clear() Clears this hashtable so that it contains no keys. |
java.lang.Object |
clone() Creates a shallow copy of this hashtable. |
boolean |
contains(java.lang.Object value) Tests if some key maps into the specified value in this hashtable. |
boolean |
containsKey(java.lang.Object key) Tests if the specified object is a key in this hashtable. |
java.util.Enumeration |
elements() Returns an enumeration of the values in this hashtable. |
java.lang.Object |
get(java.lang.Object key) Returns the value to which the specified key is mapped in this hashtable. |
boolean |
isEmpty() Tests if this hashtable maps no keys to values. |
java.util.Enumeration |
keys() Returns an enumeration of the keys in this hashtable. |
java.lang.Object |
put(java.lang.Object key, java.lang.Object value) Maps the specified key to the specified value in this hashtable. |
protected void |
rehash() Rehashes the contents of the hashtable into a hashtable with a larger capacity. |
java.lang.Object |
remove(java.lang.Object key) Removes the key (and its corresponding value) from this hashtable. |
int |
size() Returns the number of keys in this hashtable. |
java.lang.String |
toString() Returns a rather long string representation of this hashtable. |
Methods inherited from class java.lang.Object |
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equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public UnsyncHashtable(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 UnsyncHashtable(int initialCapacity)
initialCapacity
- the initial capacity of the hashtable.public UnsyncHashtable()
Method Detail |
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public int size()
size
in class java.util.Dictionary
public boolean isEmpty()
isEmpty
in class java.util.Dictionary
true
if this hashtable maps no keys to values; false
otherwise.public java.util.Enumeration keys()
keys
in class java.util.Dictionary
public java.util.Enumeration elements()
elements
in class java.util.Dictionary
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 hashtable; false
otherwise.java.lang.NullPointerException
- if the value is null
.public boolean containsKey(java.lang.Object key)
key
- possible key.true
if the specified object is a key in this hashtable; false
otherwise.public java.lang.Object get(java.lang.Object key)
get
in class java.util.Dictionary
key
- a key in the hashtable.null
if the key is not mapped to any value in this hashtable.protected void rehash()
public java.lang.Object put(java.lang.Object key, java.lang.Object value)
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.
put
in class java.util.Dictionary
key
- the hashtable key.value
- the value.null
if it did not have one.java.lang.NullPointerException
- if the key or value is null
.public java.lang.Object remove(java.lang.Object key)
remove
in class java.util.Dictionary
key
- the key that needs to be removed.null
if the key did not have a mapping.public void clear()
public java.lang.Object clone()
clone
in class java.lang.Object
public java.lang.String toString()
toString
in class java.lang.Object
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Oracle Security Developer Tools Crypto FIPS Java API Reference 11g (11.1.1) E10696-02 |
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