WeakIdentityMap (Lucene 3.6.2 API)

java.lang.Object
- org.apache.lucene.util.WeakIdentityMap<K,V>

```
public final class WeakIdentityMap<K,V>
extends Object
```
Implements a combination of WeakHashMap and IdentityHashMap. Useful for caches that need to key off of a == comparison instead of a .equals.
This class is not a general-purpose Map implementation! It intentionally violates Map's general contract, which mandates the use of the equals method when comparing objects. This class is designed for use only in the rare cases wherein reference-equality semantics are required.
This implementation was forked from Apache CXF but modified to not implement the Map interface and without any set views on it, as those are error-prone and inefficient, if not implemented carefully. The map only contains Iterator implementations on the values and not-GCed keys. Lucene's implementation also supports null keys, but those are never weak!

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`clear()`
`boolean`	`containsKey(Object key)`
`V`	`get(Object key)`
`boolean`	`isEmpty()`
`Iterator<K>`	`keyIterator()`	Returns an iterator over all weak keys of this map.
`static <K,V> WeakIdentityMap<K,V>`	`newConcurrentHashMap()`	Creates a new `WeakIdentityMap` based on a `ConcurrentHashMap`.
`static <K,V> WeakIdentityMap<K,V>`	`newHashMap()`	Creates a new `WeakIdentityMap` based on a non-synchronized `HashMap`.
`V`	`put(K key, V value)`
`V`	`remove(Object key)`
`int`	`size()`
`Iterator<V>`	`valueIterator()`	Returns an iterator over all values of this map.

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

- Method Detail
  - newHashMap
```
public static final <K,V> WeakIdentityMap<K,V> newHashMap()
```
    Creates a new WeakIdentityMap based on a non-synchronized HashMap.
  - newConcurrentHashMap
```
public static final <K,V> WeakIdentityMap<K,V> newConcurrentHashMap()
```
    Creates a new WeakIdentityMap based on a ConcurrentHashMap.
  - clear
```
public void clear()
```
  - containsKey
```
public boolean containsKey(Object key)
```
  - get
```
public V get(Object key)
```
  - put
```
public V put(K key,
             V value)
```
  - isEmpty
```
public boolean isEmpty()
```
  - remove
```
public V remove(Object key)
```
  - size
```
public int size()
```
  - keyIterator
```
public Iterator<K> keyIterator()
```
    Returns an iterator over all weak keys of this map. Keys already garbage collected will not be returned. This Iterator does not support removals.
  - valueIterator
```
public Iterator<V> valueIterator()
```
    Returns an iterator over all values of this map. This iterator may return values whose key is already garbage collected while iterator is consumed.