LRUMap (jackson-databind 2.4.0)

java.lang.Object
- java.util.AbstractMap<K,V>
- - java.util.HashMap<K,V>
  - - java.util.LinkedHashMap<K,V>
    - - com.fasterxml.jackson.databind.util.LRUMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>
```
public class LRUMap<K,V>
extends LinkedHashMap<K,V>
implements Serializable
```
Helper for simple bounded LRU maps used for reusing lookup values.
Note that serialization behavior is such that contents are NOT serialized, on assumption that all use cases are for caching where persistence does not make sense. The only thing serialized is the cache size of Map.
NOTE: the only reason we extend LinkedHashMap instead of aggregating it is that this way we can override removeEldestEntry(java.util.Map.Entry<K, V>). Access, however, MUST be done using single-element access methods (or matching xxxAll() methods that call them); access via iterators are not guaranteed to work.
NOTE: since version 2.4, uses ReentrantReadWriteLock to improve concurrent access.

See Also:
Serialized Form

Nested Class Summary
- Nested classes/interfaces inherited from class java.util.AbstractMap
  AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Field Summary

Fields
Modifier and Type	Field and Description
`protected int`	`_jdkSerializeMaxEntries` Ugly hack, to work through the requirement that _value is indeed final, and that JDK serialization won't call ctor(s) if Serializable is implemented.
`protected int`	`_maxEntries`
`protected Lock`	`_readLock`
`protected Lock`	`_writeLock`

Constructor Summary

Constructors
Constructor and Description

LRUMap(int initialEntries, int maxEntries)

Method Summary

Methods
Modifier and Type	Method and Description
`V`	`get(Object key)`
`V`	`put(K key, V value)`
`protected Object`	`readResolve()`
`V`	`remove(Object key)`
`protected boolean`	`removeEldestEntry(Map.Entry<K,V> eldest)`

Methods inherited from class java.util.LinkedHashMap
clear, containsValue

Methods inherited from class java.util.HashMap
clone, containsKey, entrySet, isEmpty, keySet, putAll, 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
containsKey, entrySet, equals, hashCode, isEmpty, keySet, putAll, size, values

- Field Detail
  - _readLock
```
protected final transient Lock _readLock
```
  - _writeLock
```
protected final transient Lock _writeLock
```
  - _maxEntries
```
protected final transient int _maxEntries
```
  - _jdkSerializeMaxEntries
```
protected transient int _jdkSerializeMaxEntries
```
    Ugly hack, to work through the requirement that _value is indeed final, and that JDK serialization won't call ctor(s) if Serializable is implemented.
    
    Since:
    
    2.1
- Constructor Detail
  - LRUMap
```
public LRUMap(int initialEntries,
      int maxEntries)
```
- Method Detail
  - removeEldestEntry
```
protected boolean removeEldestEntry(Map.Entry<K,V> eldest)
```
    Overrides:
    
    removeEldestEntry in class LinkedHashMap<K,V>
  - get
```
public V get(Object key)
```
    Specified by:
    
    get in interface Map<K,V>
    
    Overrides:
    
    get in class LinkedHashMap<K,V>
  - put
```
public V put(K key,
    V value)
```
    Specified by:
    
    put in interface Map<K,V>
    
    Overrides:
    
    put in class HashMap<K,V>
  - remove
```
public V remove(Object key)
```
    Specified by:
    
    remove in interface Map<K,V>
    
    Overrides:
    
    remove in class HashMap<K,V>
  - readResolve
```
protected Object readResolve()
```

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