Long2ObjectCache (Agrona)

java.lang.Object
- org.agrona.collections.Long2ObjectCache<V>

Type Parameters:

V - type of values stored in the Map

All Implemented Interfaces:

Serializable, Map<Long,V>
```
public class Long2ObjectCache<V>
extends Object
implements Map<Long,V>, Serializable
```
A cache implementation specialised for long keys using open addressing to probe a set of fixed size.
The eviction strategy is to remove the oldest in a set if the key is not found, or if found then that item. The newly inserted item becomes the youngest in the set. Sets are evicted on a first in, first out, manner unless replacing a matching key.
A good set size would be in the range of 2 to 16 so that the references/keys can fit in a cache-line (assuming references are 32 bit references and 64 byte cache lines, YMMV). A linear search within a cache line is much much less costly than a cache-miss to another line.
Null values are not supported by this cache.

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`class`	`Long2ObjectCache.EntryIterator`
`class`	`Long2ObjectCache.EntrySet`
`class`	`Long2ObjectCache.KeyIterator`
`class`	`Long2ObjectCache.KeySet`
`class`	`Long2ObjectCache.ValueCollection`
`class`	`Long2ObjectCache.ValueIterator`

Nested classes/interfaces inherited from interface java.util.Map
Map.Entry<K,V>

Constructor Summary

Constructors
Constructor and Description

Long2ObjectCache(int numSets, int setSize, Consumer<V> evictionConsumer)

Constructors
Constructor and Description
`Long2ObjectCache(int numSets, int setSize, Consumer<V> evictionConsumer)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`long`	`cacheHits()` The number of times a cache hit has occurred on the `get(long)` method.
`long`	`cacheMisses()` The number of times a cache miss has occurred on the `get(long)` method.
`long`	`cachePuts()` The number of items that have been put in the cache.
`int`	`capacity()` Get the total capacity for the map to which the load factor will be a fraction of.
`void`	`clear()` Clear down all items in the cache.
`V`	`computeIfAbsent(long key, LongFunction<? extends V> mappingFunction)` Get a value for a given key, or if it does ot exist then default the value via a `LongFunction` and put it in the cache.
`boolean`	`containsKey(long key)` Overloaded version of `Map.containsKey(Object)` that takes a primitive long key.
`boolean`	`containsKey(Object key)`
`boolean`	`containsValue(Object value)`
`Long2ObjectCache.EntrySet`	`entrySet()`
`boolean`	`equals(Object o)`
`V`	`get(long key)` Overloaded version of `Map.get(Object)` that takes a primitive long key.
`V`	`get(Object key)`
`int`	`hashCode()`
`boolean`	`isEmpty()`
`Long2ObjectCache.KeySet`	`keySet()`
`V`	`put(long key, V value)` Overloaded version of `Map.put(Object, Object)` that takes a primitive long key.
`V`	`put(Long key, V value)`
`void`	`putAll(Map<? extends Long,? extends V> map)`
`V`	`remove(long key)` Overloaded version of `Map.remove(Object)` that takes a primitive long key.
`V`	`remove(Object key)`
`void`	`resetCounters()` Reset the cache statistics counters to zero.
`int`	`size()`
`String`	`toString()`
`Long2ObjectCache.ValueCollection`	`values()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

- Constructor Detail
  - Long2ObjectCache
```
public Long2ObjectCache(int numSets,
                        int setSize,
                        Consumer<V> evictionConsumer)
```
- Method Detail
  - cacheHits
```
public long cacheHits()
```
    The number of times a cache hit has occurred on the get(long) method.
    
    Returns:
    
    the number of times a cache hit has occurred on the get(long) method.
  - cacheMisses
```
public long cacheMisses()
```
    The number of times a cache miss has occurred on the get(long) method.
    
    Returns:
    
    the number of times a cache miss has occurred on the get(long) method.
  - cachePuts
```
public long cachePuts()
```
    The number of items that have been put in the cache.
    
    Returns:
    
    number of items that have been put in the cache.
  - resetCounters
```
public void resetCounters()
```
    Reset the cache statistics counters to zero.
  - capacity
```
public int capacity()
```
    Get the total capacity for the map to which the load factor will be a fraction of.
    
    Returns:
    
    the total capacity for the map.
  - size
```
public int size()
```
    Specified by:
    
    size in interface Map<Long,V>
  - isEmpty
```
public boolean isEmpty()
```
    Specified by:
    
    isEmpty in interface Map<Long,V>
  - containsKey
```
public boolean containsKey(Object key)
```
    Specified by:
    
    containsKey in interface Map<Long,V>
  - containsKey
```
public boolean containsKey(long key)
```
    Overloaded version of Map.containsKey(Object) that takes a primitive long key.
    
    Parameters:
    
    key - for indexing the Map
    
    Returns:
    
    true if the key is found otherwise false.
  - containsValue
```
public boolean containsValue(Object value)
```
    Specified by:
    
    containsValue in interface Map<Long,V>
  - get
```
public V get(Object key)
```
    Specified by:
    
    get in interface Map<Long,V>
  - get
```
public V get(long key)
```
    Overloaded version of Map.get(Object) that takes a primitive long key.
    
    Parameters:
    
    key - for indexing the Map
    
    Returns:
    
    the value if found otherwise null
  - computeIfAbsent
```
public V computeIfAbsent(long key,
                         LongFunction<? extends V> mappingFunction)
```
    Get a value for a given key, or if it does ot exist then default the value via a LongFunction and put it in the cache.
    Primitive specialized version of Map.computeIfAbsent(K, java.util.function.Function<? super K, ? extends V>).
    
    Parameters:
    
    key - to search on.
    
    mappingFunction - to provide a value if the get returns null.
    
    Returns:
    
    the value if found otherwise the default.
  - put
```
public V put(Long key,
             V value)
```
    Specified by:
    
    put in interface Map<Long,V>
  - put
```
public V put(long key,
             V value)
```
    Overloaded version of Map.put(Object, Object) that takes a primitive long key.
    
    Parameters:
    
    key - for indexing the Map
    
    value - to be inserted in the Map
    
    Returns:
    
    always null (as per JCache API, as opposed to Map)
  - remove
```
public V remove(Object key)
```
    Specified by:
    
    remove in interface Map<Long,V>
  - remove
```
public V remove(long key)
```
    Overloaded version of Map.remove(Object) that takes a primitive long key.
    
    Parameters:
    
    key - for indexing the Map
    
    Returns:
    
    the value if found otherwise null
  - clear
```
public void clear()
```
    Clear down all items in the cache.
    If an exception occurs during the eviction function callback then clear may need to be called again to complete.
    If an exception occurs the cache should only be used when size() reports zero.
    
    Specified by:
    
    clear in interface Map<Long,V>
  - putAll
```
public void putAll(Map<? extends Long,? extends V> map)
```
    Specified by:
    
    putAll in interface Map<Long,V>
  - keySet
```
public Long2ObjectCache.KeySet keySet()
```
    Specified by:
    
    keySet in interface Map<Long,V>
  - values
```
public Long2ObjectCache.ValueCollection values()
```
    Specified by:
    
    values in interface Map<Long,V>
  - entrySet
```
public Long2ObjectCache.EntrySet entrySet()
```
    Specified by:
    
    entrySet in interface Map<Long,V>
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - equals
```
public boolean equals(Object o)
```
    Specified by:
    
    equals in interface Map<Long,V>
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface Map<Long,V>
    
    Overrides:
    
    hashCode in class Object

Class Long2ObjectCache<V>

Nested Class Summary

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

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Constructor Detail

Long2ObjectCache

Method Detail

cacheHits

cacheMisses

cachePuts

resetCounters

capacity

size

isEmpty

containsKey

containsKey

containsValue

get

get

computeIfAbsent

put

put

remove

remove

clear

putAll

keySet

values

entrySet

toString

equals

hashCode