com.google.cloud.bigtable.util

Class ReferenceCountedHashMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

com.google.cloud.bigtable.util.ReferenceCountedHashMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

@InternalApi
public class ReferenceCountedHashMap<K,V>
extends HashMap<K,V>

Allows for a HashMap to reference-count its contents.

Specifically we have subclassed only the methods related to placement and removal. Though there is more functionality which could be used from Java8, we have chosen to not subclass them as we are not expecting their use as of now. Other items have not been subclassed as they do not affect reference counts (e.g.: get).

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ReferenceCountedHashMap.Callable<I> Interface for destructor code.

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
ReferenceCountedHashMap() Constructor for ReferenceCountedHashMap.
ReferenceCountedHashMap(ReferenceCountedHashMap.Callable<V> cleanerCallable) Constructor for ReferenceCountedHashMap wth a destructor callable.

Method Summary

Modifier and Type	Method and Description
void	clear() Remove all items from hash map and all references from reference counter.
Object	clone()
V	put(K key, V value) Put inserts a key-value pair into the map.
void	putAll(Map<? extends K,? extends V> m)
V	remove(Object key) Remove removes a reference to the key within the context of the reference count.

Methods inherited from class java.util.HashMap

compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, forEach, get, getOrDefault, isEmpty, keySet, merge, putIfAbsent, remove, replace, replace, replaceAll, size, values

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

equals, hashCode

Constructor Detail

ReferenceCountedHashMap

public ReferenceCountedHashMap()

Constructor for ReferenceCountedHashMap.

ReferenceCountedHashMap

public ReferenceCountedHashMap(ReferenceCountedHashMap.Callable<V> cleanerCallable)

Constructor for ReferenceCountedHashMap wth a destructor callable.

Method Detail

put

public V put(K key,
             V value)

Put inserts a key-value pair into the map. If the pair is new, we instantiate its reference count and place the pair into the map; otherwise we just increment it (without placement).

Specified by:

put in interface Map<K,V>

Overrides:

put in class HashMap<K,V>

Parameters:

key - The key component of the key-value pair.

value - The pair component of the key-value pair.

Returns:

The value inserted.

remove

public V remove(Object key)

Remove removes a reference to the key within the context of the reference count. If no references are left, it also removes the pair from the underlying HashMap.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class HashMap<K,V>

Parameters:

key - The key for which the reference should be removed.

Returns:

The value removed, or null if it does not exist.

clear

public void clear()

Remove all items from hash map and all references from reference counter.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class HashMap<K,V>

clone

public Object clone()

Overrides:

clone in class HashMap<K,V>

putAll

public void putAll(Map<? extends K,? extends V> m)

Specified by:

putAll in interface Map<K,V>

Overrides:

putAll in class HashMap<K,V>