Top Description Inners Fields Constructors Methods
org.apache.avro.util

public Class WeakIdentityHashMap<K, V>

extends Object
implements Map<K, V>
Class Inheritance
All Implemented Interfaces
java.util.Map
Imports
java.lang.ref.ReferenceQueue, .WeakReference, java.util.Collection, .Collections, .HashMap, .HashSet, .Map, .Set
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! While this class implements the Map interface, 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. Note that this implementation is not synchronized.

Nested and Inner Type Summary

Modifier and TypeClass and Description
pack-priv class
WeakIdentityHashMap.IdentityWeakReference

Field Summary

Modifier and TypeField and Description
private Map<WeakIdentityHashMap<K, V>.IdentityWeakReference, V>
backingStore

private final ReferenceQueue<K>
queue

Constructor Summary

AccessConstructor and Description
public
WeakIdentityHashMap()

Method Summary

Modifier and TypeMethod and Description
public void
clear()

Implements java.util.Map.clear.

Removes all of the mappings from this map (optional operation).
public boolean
containsKey(Object
key whose presence in this map is to be tested
key)

Implements java.util.Map.containsKey.

Returns true if this map contains a mapping for the specified key.
public boolean
containsValue(Object
value whose presence in this map is to be tested
value)

Implements java.util.Map.containsValue.

Returns true if this map maps one or more keys to the specified value.
public Set<Map.Entry<K, V>>
entrySet()

Implements java.util.Map.entrySet.

Returns a Set view of the mappings contained in this map.
public boolean
equals(Object
object to be compared for equality with this map
o)

Overrides java.lang.Object.equals.

Implements java.util.Map.equals.

Compares the specified object with this map for equality.
public V
get(Object
the key whose associated value is to be returned
key)

Implements java.util.Map.get.

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
public int
hashCode()

Overrides java.lang.Object.hashCode.

Implements java.util.Map.hashCode.

Returns the hash code value for this map.
public boolean
isEmpty()

Implements java.util.Map.isEmpty.

Returns true if this map contains no key-value mappings.
public Set<K>
keySet()

Implements java.util.Map.keySet.

Returns a Set view of the keys contained in this map.
public V
put(K
key with which the specified value is to be associated
key, V
value to be associated with the specified key
value)

Implements java.util.Map.put.

Associates the specified value with the specified key in this map (optional operation).
public void
putAll(Map<K, V>
mappings to be stored in this map
t)

Implements java.util.Map.putAll.

Copies all of the mappings from the specified map to this map (optional operation).
private synchronized void
reap()

public V
remove(Object
key whose mapping is to be removed from the map
key)

Implements java.util.Map.remove.

Removes the mapping for a key from this map if it is present (optional operation).
public int
size()

Implements java.util.Map.size.

Returns the number of key-value mappings in this map.
public Collection<V>
values()

Implements java.util.Map.values.

Returns a Collection view of the values contained in this map.
Inherited from java.lang.Object:
clonefinalizegetClassnotifynotifyAlltoStringwaitwaitwait

Field Detail

backingStoreback to summary
private Map<WeakIdentityHashMap<K, V>.IdentityWeakReference, V> backingStore
queueback to summary
private final ReferenceQueue<K> queue

Constructor Detail

WeakIdentityHashMapback to summary
public WeakIdentityHashMap()

Method Detail

clearback to summary
public void clear()

Implements java.util.Map.clear.

Doc from java.util.Map.clear.

Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.

Annotations
@Override
containsKeyback to summary
public boolean containsKey(Object key)

Implements java.util.Map.containsKey.

Doc from java.util.Map.containsKey.

Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that Objects.equals(key, k). (There can be at most one such mapping.)

Parameters
key:Object

key whose presence in this map is to be tested

Returns:boolean

true if this map contains a mapping for the specified key

Annotations
@Override
containsValueback to summary
public boolean containsValue(Object value)

Implements java.util.Map.containsValue.

Doc from java.util.Map.containsValue.

Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that Objects.equals(value, v). This operation will probably require time linear in the map size for most implementations of the Map interface.

Parameters
value:Object

value whose presence in this map is to be tested

Returns:boolean

true if this map maps one or more keys to the specified value

Annotations
@Override
entrySetback to summary
public Set<Map.Entry<K, V>> entrySet()

Implements java.util.Map.entrySet.

Doc from java.util.Map.entrySet.

Returns a Set view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns:Set<Map.Entry<K, V>>

a set view of the mappings contained in this map

Annotations
@Override
equalsback to summary
public boolean equals(Object o)

Overrides java.lang.Object.equals.

Implements java.util.Map.equals.

Doc from java.util.Map.equals.

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.

Parameters
o:Object

object to be compared for equality with this map

Returns:boolean

true if the specified object is equal to this map

Annotations
@Override
getback to summary
public V get(Object key)

Implements java.util.Map.get.

Doc from java.util.Map.get.

Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

More formally, if this map contains a mapping from a key k to a value v such that Objects.equals(key, k), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Parameters
key:Object

the key whose associated value is to be returned

Returns:V

the value to which the specified key is mapped, or null if this map contains no mapping for the key

Annotations
@Override
hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Implements java.util.Map.hashCode.

Doc from java.util.Map.hashCode.

Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hash codes of each entry in the map's entrySet() view. This ensures that m1.equals(m2) implies that m1.hashCode()==m2.hashCode() for any two maps m1 and m2, as required by the general contract of Object#hashCode.

Returns:int

the hash code value for this map

Annotations
@Override
isEmptyback to summary
public boolean isEmpty()

Implements java.util.Map.isEmpty.

Doc from java.util.Map.isEmpty.

Returns true if this map contains no key-value mappings.

Returns:boolean

true if this map contains no key-value mappings

Annotations
@Override
keySetback to summary
public Set<K> keySet()

Implements java.util.Map.keySet.

Doc from java.util.Map.keySet.

Returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Returns:Set<K>

a set view of the keys contained in this map

Annotations
@Override
putback to summary
public V put(K key, V value)

Implements java.util.Map.put.

Doc from java.util.Map.put.

Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)

Parameters
key:K

key with which the specified value is to be associated

value:V

value to be associated with the specified key

Returns:V

the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

Annotations
@Override
putAllback to summary
public void putAll(Map<K, V> t)

Implements java.util.Map.putAll.

Doc from java.util.Map.putAll.

Copies all of the mappings from the specified map to this map (optional operation). The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress. If the specified map has a defined encounter order, processing of its mappings generally occurs in that order.

Parameters
t:Map<K, V>

mappings to be stored in this map

Annotations
@Override
reapback to summary
private synchronized void reap()
removeback to summary
public V remove(Object key)

Implements java.util.Map.remove.

Doc from java.util.Map.remove.

Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that Objects.equals(key, k), that mapping is removed. (The map can contain at most one such mapping.)

Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.

If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

The map will not contain a mapping for the specified key once the call returns.

Parameters
key:Object

key whose mapping is to be removed from the map

Returns:V

the previous value associated with key, or null if there was no mapping for key.

Annotations
@Override
sizeback to summary
public int size()

Implements java.util.Map.size.

Doc from java.util.Map.size.

Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Returns:int

the number of key-value mappings in this map

Annotations
@Override
valuesback to summary
public Collection<V> values()

Implements java.util.Map.values.

Doc from java.util.Map.values.

Returns a Collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns:Collection<V>

a collection view of the values contained in this map

Annotations
@Override
org.apache.avro.util back to summary

pack-priv Class WeakIdentityHashMap.IdentityWeakReference

extends WeakReference<K>
Class Inheritance

Field Summary

Modifier and TypeField and Description
pack-priv int
hash

Constructor Summary

AccessConstructor and Description
pack-priv
IdentityWeakReference(Object obj)

Method Summary

Modifier and TypeMethod and Description
public boolean
equals(Object
the reference object with which to compare.
o)

Overrides java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.
public int
hashCode()

Overrides java.lang.Object.hashCode.

Returns a hash code value for the object.

Field Detail

hashback to summary
pack-priv int hash

Constructor Detail

IdentityWeakReferenceback to summary
pack-priv IdentityWeakReference(Object obj)
Annotations
@SuppressWarnings:unchecked

Method Detail

equalsback to summary
public boolean equals(Object o)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Parameters
o:Object

the reference object with which to compare.

Returns:boolean

true if this object is the same as the obj argument; false otherwise.

Annotations
@Override
hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by java.util.HashMap.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
Returns:int

a hash code value for this object.

Annotations
@Override