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Class Acme.LruHashtable

java.lang.Object
   |
   +----java.util.Dictionary
           |
           +----java.util.Hashtable
                   |
                   +----Acme.LruHashtable

public class LruHashtable

extends Hashtable

Use just like java.util.Hashtable, except that the initial-capacity parameter is required. Instead of growing bigger than that size, it will throw out objects that haven't been looked at in a while.

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See Also:

Hashtable

LruHashtable(int)

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

LruHashtable(int, float)

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

clear()

Clears the hash table so that it has no more elements in it.

clone()

Creates a clone of the hashtable.

contains(Object)

Returns true if the specified object is an element of the hashtable.

containsKey(Object)

Returns true if the collection contains an element for the key.

elements()

Returns an enumeration of the elements.

get(Object)

Gets the object associated with the specified key in the hashtable.

isEmpty()

Returns true if the hashtable contains no elements.

keys()

Returns an enumeration of the hashtable's keys.

put(Object, Object)

Puts the specified element into the hashtable, using the specified key.

remove(Object)

Removes the element corresponding to the key.

size()

Returns the number of elements contained in the hashtable.

 public LruHashtable(int initialCapacity,
                     float loadFactor)

Constructs a new, empty hashtable with the specified initial capacity and the specified load factor. Unlike a plain Hashtable, an LruHashtable will never grow or shrink from this initial capacity.

Parameters:

initialCapacity - the initial number of buckets

loadFactor - a number between 0.0 and 1.0, it defines the threshold for expiring old entries

Throws: IllegalArgumentException

If the initial capacity is less than or equal to zero.

Throws: IllegalArgumentException

If the load factor is less than or equal to zero.

 public LruHashtable(int initialCapacity)

Constructs a new, empty hashtable with the specified initial capacity. Unlike a plain Hashtable, an LruHashtable will never grow or shrink from this initial capacity.

Parameters:

initialCapacity - the initial number of buckets

 public int size()

Returns the number of elements contained in the hashtable.

Overrides:

size in class Hashtable

 public boolean isEmpty()

Returns true if the hashtable contains no elements.

Overrides:

isEmpty in class Hashtable

 public synchronized Enumeration keys()

Returns an enumeration of the hashtable's keys.

Overrides:

keys in class Hashtable

See Also:

elements, Enumeration

 public synchronized Enumeration elements()

Returns an enumeration of the elements. Use the Enumeration methods on the returned object to fetch the elements sequentially.

Overrides:

elements in class Hashtable

See Also:

keys, Enumeration

 public synchronized boolean contains(Object value)

Returns true if the specified object is an element of the hashtable. This operation is more expensive than the containsKey() method.

Parameters:

value - the value that we are looking for

Throws: NullPointerException

If the value being searched for is equal to null.

Overrides:

contains in class Hashtable

See Also:

containsKey

 public synchronized boolean containsKey(Object key)

Returns true if the collection contains an element for the key.

Parameters:

key - the key that we are looking for

Overrides:

containsKey in class Hashtable

See Also:

contains

 public synchronized Object get(Object key)

Gets the object associated with the specified key in the hashtable.

Parameters:

key - the specified key

Returns:

s the element for the key or null if the key is not defined in the hash table.

Overrides:

get in class Hashtable

See Also:

put

 public synchronized Object put(Object key,
                                Object value)

Puts the specified element into the hashtable, using the specified key. The element may be retrieved by doing a get() with the same key. The key and the element cannot be null.

Parameters:

key - the specified key in the hashtable

value - the specified element

Returns:

the old value of the key, or null if it did not have one.

Throws: NullPointerException

If the value of the element is equal to null.

Overrides:

put in class Hashtable

See Also:

get

 public synchronized Object remove(Object key)

Removes the element corresponding to the key. Does nothing if the key is not present.

Parameters:

key - the key that needs to be removed

Returns:

the value of key, or null if the key was not found.

Overrides:

remove in class Hashtable

 public synchronized void clear()

Clears the hash table so that it has no more elements in it.

Overrides:

clear in class Hashtable

 public synchronized Object clone()

Creates a clone of the hashtable. A shallow copy is made, the keys and elements themselves are NOT cloned. This is a relatively expensive operation.

Overrides:

clone in class Hashtable

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