Cache

extends Object

java.lang.Object
↳	sun.security.util.Cache

Class Overview

Abstract base class and factory for caches. A cache is a key-value mapping. It has properties that make it more suitable for caching than a Map. The factory methods can be used to obtain two different implementations. They have the following properties: . keys and values reside in memory . keys and values must be non-null . maximum size. Replacements are made in LRU order. . optional lifetime, specified in seconds. . save for concurrent use by multiple threads . values are held by either standard references or via SoftReferences. SoftReferences have the advantage that they are automatically cleared by the garbage collector in response to memory demand. This makes it possible to simple set the maximum size to a very large value and let the GC automatically size the cache dynamically depending on the amount of available memory. However, note that because of the way SoftReferences are implemented in HotSpot at the moment, this may not work perfectly as it clears them fairly eagerly. Performance may be improved if the Java heap size is set to larger value using e.g. java -ms64M -mx128M foo.Test Cache sizing: the memory cache is implemented on top of a LinkedHashMap. In its current implementation, the number of buckets (NOT entries) in (Linked)HashMaps is always a power of two. It is recommended to set the maximum cache size to value that uses those buckets fully. For example, if a cache with somewhere between 500 and 1000 entries is desired, a maximum size of 750 would be a good choice: try 1024 buckets, with a load factor of 0.75f, the number of entries can be calculated as buckets / 4 * 3. As mentioned above, with a SoftReference cache, it is generally reasonable to set the size to a fairly large value.

Summary

Nested Classes
class	Cache.EqualByteArray	Utility class that wraps a byte array and implements the equals() and hashCode() contract in a way suitable for Maps and caches.

Protected Constructors
	Cache()

Public Methods
abstract void	clear() Remove all entries from the cache.
abstract Object	get(Object key) Get a value from the cache.
static Cache	newHardMemoryCache(int size, int timeout) Return a new memory cache with the specified maximum size, the specified maximum lifetime (in seconds), with the values held by standard references.
static Cache	newHardMemoryCache(int size) Return a new memory cache with the specified maximum size, unlimited lifetime for entries, with the values held by standard references.
static Cache	newNullCache() Return a dummy cache that does nothing.
static Cache	newSoftMemoryCache(int size) Return a new memory cache with the specified maximum size, unlimited lifetime for entries, with the values held by SoftReferences.
static Cache	newSoftMemoryCache(int size, int timeout) Return a new memory cache with the specified maximum size, the specified maximum lifetime (in seconds), with the values held by SoftReferences.
abstract void	put(Object key, Object value) Add an entry to the cache.
abstract void	remove(Object key) Remove an entry from the cache.
abstract int	size() Return the number of currently valid entries in the cache.

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Inherited Methods

From class java.lang.Object

Object	clone() Creates and returns a copy of this object.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
final Class<?>	getClass() Returns the runtime class of this `Object`.
int	hashCode() Returns a hash code value for the object.
final void	notify() Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll() Wakes up all threads that are waiting on this object's monitor.
String	toString() Returns a string representation of the object.
final void	wait() Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.
final void	wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
final void	wait(long timeout) Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.

Protected Constructors

protected Cache ()

Public Methods

public abstract void clear ()

Remove all entries from the cache.

public abstract Object get (Object key)

Get a value from the cache.

public static Cache newHardMemoryCache (int size, int timeout)

Return a new memory cache with the specified maximum size, the specified maximum lifetime (in seconds), with the values held by standard references.

public static Cache newHardMemoryCache (int size)

Return a new memory cache with the specified maximum size, unlimited lifetime for entries, with the values held by standard references.

public static Cache newNullCache ()

Return a dummy cache that does nothing.

public static Cache newSoftMemoryCache (int size)

Return a new memory cache with the specified maximum size, unlimited lifetime for entries, with the values held by SoftReferences.

public static Cache newSoftMemoryCache (int size, int timeout)

Return a new memory cache with the specified maximum size, the specified maximum lifetime (in seconds), with the values held by SoftReferences.

public abstract void put (Object key, Object value)

Add an entry to the cache.

public abstract void remove (Object key)

Remove an entry from the cache.

public abstract int size ()

Return the number of currently valid entries in the cache.

Interfaces

Classes

Exceptions