com.espertech.esper.collection

Class RefCountedMap<K,V>

java.lang.Object

com.espertech.esper.collection.RefCountedMap<K,V>

public class RefCountedMap<K,V>
extends Object

Reference-counting map based on a HashMap implementation that stores as a value a pair of value and reference counter. The class provides a reference method that takes a key and increments the reference count for the key. It also provides a de-reference method that takes a key and decrements the reference count for the key, and removes the key if the reference count reached zero. Null values are not allowed as keys.

Constructor Summary

Constructors

Constructor and Description
RefCountedMap() Constructor.

Method Summary

Modifier and Type	Method and Description
void	clear() Clear out the collection.
boolean	dereference(K key) Decreases the reference count for a given key by one.
V	get(K key) Get the value for a given key, returning null if the key was not found.
V	put(K key, V value) Add and key and value with a reference count as one.
void	reference(K key) Increase the reference count for a given key by one.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RefCountedMap

public RefCountedMap()

Constructor.

Method Detail

put

public V put(K key,
             V value)

Add and key and value with a reference count as one. If the key already exists, throw an exception. Clients should use the "get" method first to check if the key exists.

Parameters:

key - to add

value - to add

Returns:

value added

get

public V get(K key)

Get the value for a given key, returning null if the key was not found.

Parameters:

key - is the key to look up and return the value for

Returns:

value for key, or null if key was not found

reference

public void reference(K key)

Increase the reference count for a given key by one. Throws an IllegalArgumentException if the key was not found.

Parameters:

key - is the key to increase the ref count for

dereference

public boolean dereference(K key)

Decreases the reference count for a given key by one. Returns true if the reference count reaches zero. Removes the key from the collection when the reference count reaches zero. Throw an IllegalArgumentException if the key is not found.

Parameters:

key - to de-reference

Returns:

true to indicate the reference count reached zero, false to indicate more references to the key exist.

clear

public void clear()

Clear out the collection.