CacheMap

extends WeakHashMap<K, V>

java.lang.Object
↳	java.util.AbstractMap<K, V>
	↳	java.util.WeakHashMap<K, V>
		↳	com.sun.jmx.remote.util.CacheMap<K, V>

Class Overview

Like WeakHashMap, except that the keys of the n most recently-accessed entries are kept as soft references. Accessing an element means creating it, or retrieving it with get. Because these entries are kept with soft references, they will tend to remain even if their keys are not referenced elsewhere. But if memory is short, they will be removed.

Summary

Public Constructors
	CacheMap(int nSoftReferences) Create a `CacheMap` that can keep up to `nSoftReferences` as soft references.

Public Methods
V	get(Object key) Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
V	put(K key, V value) Associates the specified value with the specified key in this map.

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Inherited Methods

From class java.util.WeakHashMap

void	clear() Removes all of the mappings from this map.
boolean	containsKey(Object key) Returns `true` if this map contains a mapping for the specified key.
boolean	containsValue(Object value) Returns `true` if this map maps one or more keys to the specified value.
Set<Entry<K, V>>	entrySet() Returns a `Set` view of the mappings contained in this map.
V	get(Object key) Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
boolean	isEmpty() Returns `true` if this map contains no key-value mappings.
Set<K>	keySet() Returns a `Set` view of the keys contained in this map.
V	put(K key, V value) Associates the specified value with the specified key in this map.
void	putAll(Map<? extends K, ? extends V> m) Copies all of the mappings from the specified map to this map.
V	remove(Object key) Removes the mapping for a key from this weak hash map if it is present.
int	size() Returns the number of key-value mappings in this map.
Collection<V>	values() Returns a `Collection` view of the values contained in this map.

From class java.util.AbstractMap

void	clear() Removes all of the mappings from this map (optional operation). This implementation calls `entrySet().clear()`.
Object	clone() Returns a shallow copy of this `AbstractMap` instance: the keys and values themselves are not cloned.
boolean	containsKey(Object key) Returns `true` if this map contains a mapping for the specified key. This implementation iterates over `entrySet()` searching for an entry with the specified key.
boolean	containsValue(Object value) Returns `true` if this map maps one or more keys to the specified value. This implementation iterates over `entrySet()` searching for an entry with the specified value.
abstract Set<Entry<K, V>>	entrySet() Returns a `Set` view of the mappings contained in this map.
boolean	equals(Object o) Compares the specified object with this map for equality.
V	get(Object key) Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key. This implementation iterates over `entrySet()` searching for an entry with the specified key.
int	hashCode() Returns the hash code value for this map.
boolean	isEmpty() Returns `true` if this map contains no key-value mappings. This implementation returns `size() == 0`.
Set<K>	keySet() Returns a `Set` view of the keys contained in this map. This implementation returns a set that subclasses `AbstractSet`.
V	put(K key, V value) Associates the specified value with the specified key in this map (optional operation). This implementation always throws an `UnsupportedOperationException`.
void	putAll(Map<? extends K, ? extends V> m) Copies all of the mappings from the specified map to this map (optional operation). This implementation iterates over the specified map's `entrySet()` collection, and calls this map's `put` operation once for each entry returned by the iteration.
V	remove(Object key) Removes the mapping for a key from this map if it is present (optional operation). This implementation iterates over `entrySet()` searching for an entry with the specified key.
int	size() Returns the number of key-value mappings in this map. This implementation returns `entrySet().size()`.
String	toString() Returns a string representation of this map.
Collection<V>	values() Returns a `Collection` view of the values contained in this map. This implementation returns a collection that subclasses `AbstractCollection`.

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.

From interface java.util.Map

abstract void	clear() Removes all of the mappings from this map (optional operation).
abstract boolean	containsKey(Object key) Returns `true` if this map contains a mapping for the specified key.
abstract boolean	containsValue(Object value) Returns `true` if this map maps one or more keys to the specified value.
abstract Set<Entry<K, V>>	entrySet() Returns a `Set` view of the mappings contained in this map.
abstract boolean	equals(Object o) Compares the specified object with this map for equality.
abstract V	get(Object key) Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
abstract int	hashCode() Returns the hash code value for this map.
abstract boolean	isEmpty() Returns `true` if this map contains no key-value mappings.
abstract Set<K>	keySet() Returns a `Set` view of the keys contained in this map.
abstract V	put(K key, V value) Associates the specified value with the specified key in this map (optional operation).
abstract void	putAll(Map<? extends K, ? extends V> m) Copies all of the mappings from the specified map to this map (optional operation).
abstract V	remove(Object key) Removes the mapping for a key from this map if it is present (optional operation).
abstract int	size() Returns the number of key-value mappings in this map.
abstract Collection<V>	values() Returns a `Collection` view of the values contained in this map.

Public Constructors

public CacheMap (int nSoftReferences)

Create a CacheMap that can keep up to nSoftReferences as soft references.

Parameters

nSoftReferences	Maximum number of keys to keep as soft references. Access times for `get` and `put` have a component that scales linearly with `nSoftReferences`, so this value should not be too great.

Throws

IllegalArgumentException	if `nSoftReferences` is negative.

Public Methods

public V get (Object key)

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that (key==null ? k==null : key.equals(k)), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

A return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

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

public V put (K key, V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for this key, the old value is replaced.

Parameters

key	key with which the specified value is to be associated.
value	value to be associated with the specified key.

Returns

the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

Classes

CacheMap

Class Overview

Summary

Public Constructors

public CacheMap (int nSoftReferences)

Parameters

Throws

Public Methods

public V get (Object key)

Parameters

Returns

public V put (K key, V value)

Parameters

Returns