com.yahoo.bard.webservice.util

Class DelegatingMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<K,V>

com.yahoo.bard.webservice.util.DelegatingMap<K,V>

Type Parameters:

K - The key type for the map

V - The value type for the map

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>

Direct Known Subclasses:

ScopeMap

public class DelegatingMap<K,V>
extends LinkedHashMap<K,V>

A delegating map has a local copy (self) of keys and values and a next map to which it delegates lookups for values which it doesn't contain. Operations which remove keys from a map throw exceptions because the local map cannot alter its delegate (removing a key with remove(K k) from the map and then still having get(K k) return the value from the delegate would be very surprising behavior on a Map).

In order to support predictable iteration ordering, this extends LinkedHashMap with a modified definition of canonical ordering based on the canonical ordering of non-shadowed keys in the delegate followed by local keys in insertion order (e.g. LinkedHashMap).

See Also:

Serialized Form

Nested Class Summary

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

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

Constructor Summary

Constructors

Constructor and Description
DelegatingMap() Constructor.
DelegatingMap(Map<K,V> nextMap) Constructor.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes are not allowed: Delegating Map should be changed in a put-only fashion.
void	clearLocal() Clear the local map.
boolean	containsKey(Object key)
boolean	containsValue(Object o)
Set<Map.Entry<K,V>>	entrySet()
boolean	equals(Object o) Are these two delegating maps the same in terms of the current layer and their delegates are equal under the definition of equality for that delegate.
LinkedHashMap<K,V>	flatView() Return a non delegating map which snapshots the data visible in this delegating map, disconnected from changes to this and the underlying delegates.
V	get(Object key)
int	hashCode()
Set<K>	keySet()
V	put(K key, V value) Adds the key and value to the local map, potentially overshadowing a version in the delegate map.
V	remove(Object o) Delegating map should be changed in a put-only fashion.
V	removeLocal(K key) Remove from the local map.
int	size()
Collection<V>	values()

Methods inherited from class java.util.LinkedHashMap

forEach, getOrDefault, removeEldestEntry, replaceAll

Methods inherited from class java.util.HashMap

clone, compute, computeIfAbsent, computeIfPresent, isEmpty, merge, putAll, putIfAbsent, remove, replace, replace

Methods inherited from class java.util.AbstractMap

toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, isEmpty, merge, putAll, putIfAbsent, remove, replace, replace

Constructor Detail

DelegatingMap

public DelegatingMap()

Constructor.

Uses a LinkedHashMap as it's base map.

DelegatingMap

public DelegatingMap(@NotNull
                     Map<K,V> nextMap)

Constructor.

Parameters:

nextMap - Map to delegate to

Method Detail

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

Overrides:

get in class LinkedHashMap<K,V>

clear

public void clear()

Removes are not allowed: Delegating Map should be changed in a put-only fashion.

Specified by:

clear in interface Map<K,V>

Overrides:

clear in class LinkedHashMap<K,V>

clearLocal

public void clearLocal()

Clear the local map. This won't affect the delegate map.

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class HashMap<K,V>

containsValue

public boolean containsValue(Object o)

Specified by:

containsValue in interface Map<K,V>

Overrides:

containsValue in class LinkedHashMap<K,V>

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class LinkedHashMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

Overrides:

entrySet in class LinkedHashMap<K,V>

put

public V put(K key,
             V value)

Adds the key and value to the local map, potentially overshadowing a version in the delegate map.

Specified by:

put in interface Map<K,V>

Overrides:

put in class HashMap<K,V>

Parameters:

key - The key to the value

value - The value being stored

Returns:

the prior value from the local map (if any) or the shadowed value from the delegate (if any)

remove

public V remove(Object o)

Delegating map should be changed in a put-only fashion. Removes are not allowed.

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class HashMap<K,V>

Parameters:

o - Object to be removed

Returns:

nothing, this is not supported and throws an exception instead

removeLocal

public V removeLocal(K key)

Remove from the local map.

Parameters:

key - key whose mapping is to be removed from the map

Returns:

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

size

public int size()

Specified by:

size in interface Map<K,V>

Overrides:

size in class HashMap<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>

Overrides:

values in class LinkedHashMap<K,V>

flatView

public LinkedHashMap<K,V> flatView()

Return a non delegating map which snapshots the data visible in this delegating map, disconnected from changes to this and the underlying delegates.

Returns:

A non delegating plain-map copy of the data visible in this map

hashCode

public int hashCode()

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class AbstractMap<K,V>

equals

public boolean equals(Object o)

Are these two delegating maps the same in terms of the current layer and their delegates are equal under the definition of equality for that delegate.

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class AbstractMap<K,V>

Parameters:

o - The object being compared

Returns:

true if the object being compared has the same local values and their delegates are equal