ForwardingMap (Guava: Google Core Libraries for Java 19.0 API)

java.lang.Object
- com.google.common.collect.ForwardingObject
- - com.google.common.collect.ForwardingMap<K,V>

All Implemented Interfaces:

Map<K,V>

Direct Known Subclasses:

EnumBiMap, EnumHashBiMap, ForwardingConcurrentMap, ForwardingNavigableMap.StandardDescendingMap, ForwardingSortedMap, ImmutableClassToInstanceMap, ImmutableTypeToInstanceMap, MutableClassToInstanceMap, MutableTypeToInstanceMap
```
@GwtCompatible
public abstract class ForwardingMap<K,V>
extends ForwardingObject
implements Map<K,V>
```
A map which forwards all its method calls to another map. Subclasses should override one or more methods to modify the behavior of the backing map as desired per the decorator pattern.
Warning: The methods of ForwardingMap forward indiscriminately to the methods of the delegate. For example, overriding put(K, V) alone will not change the behavior of putAll(java.util.Map<? extends K, ? extends V>), which can lead to unexpected behavior. In this case, you should override putAll as well, either providing your own implementation, or delegating to the provided standardPutAll method.
Each of the standard methods, where appropriate, use Objects.equal(java.lang.Object, java.lang.Object) to test equality for both keys and values. This may not be the desired behavior for map implementations that use non-standard notions of key equality, such as a SortedMap whose comparator is not consistent with equals.
The standard methods and the collection views they return are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.

Since:

2.0

Author:

Kevin Bourrillion, Jared Levy, Louis Wasserman

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected class`	`ForwardingMap.StandardEntrySet` A sensible implementation of `Map.entrySet()` in terms of the following methods: `clear()`, `containsKey(java.lang.Object)`, `get(java.lang.Object)`, `isEmpty()`, `remove(java.lang.Object)`, and `size()`.
`protected class`	`ForwardingMap.StandardKeySet` A sensible implementation of `Map.keySet()` in terms of the following methods: `clear()`, `containsKey(java.lang.Object)`, `isEmpty()`, `remove(java.lang.Object)`, `size()`, and the `Set.iterator()` method of `entrySet()`.
`protected class`	`ForwardingMap.StandardValues` A sensible implementation of `Map.values()` in terms of the following methods: `clear()`, `containsValue(java.lang.Object)`, `isEmpty()`, `size()`, and the `Set.iterator()` method of `entrySet()`.

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

Constructor Summary

Constructors
Modifier Constructor and Description

protected ForwardingMap()
Constructor for use by subclasses.

Constructors
Modifier	Constructor and Description
`protected`	`ForwardingMap()` Constructor for use by subclasses.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clear()`
`boolean`	`containsKey(Object key)`
`boolean`	`containsValue(Object value)`
`protected abstract Map<K,V>`	`delegate()` Returns the backing delegate instance that methods are forwarded to.
`Set<Map.Entry<K,V>>`	`entrySet()`
`boolean`	`equals(Object object)`
`V`	`get(Object key)`
`int`	`hashCode()`
`boolean`	`isEmpty()`
`Set<K>`	`keySet()`
`V`	`put(K key, V value)`
`void`	`putAll(Map<? extends K,? extends V> map)`
`V`	`remove(Object object)`
`int`	`size()`
`protected void`	`standardClear()` A sensible definition of `clear()` in terms of the `iterator` method of `entrySet()`.
`protected boolean`	`standardContainsKey(Object key)` A sensible, albeit inefficient, definition of `containsKey(java.lang.Object)` in terms of the `iterator` method of `entrySet()`.
`protected boolean`	`standardContainsValue(Object value)` A sensible definition of `containsValue(java.lang.Object)` in terms of the `iterator` method of `entrySet()`.
`protected boolean`	`standardEquals(Object object)` A sensible definition of `equals(java.lang.Object)` in terms of the `equals` method of `entrySet()`.
`protected int`	`standardHashCode()` A sensible definition of `hashCode()` in terms of the `iterator` method of `entrySet()`.
`protected boolean`	`standardIsEmpty()` A sensible definition of `isEmpty()` in terms of the `iterator` method of `entrySet()`.
`protected void`	`standardPutAll(Map<? extends K,? extends V> map)` A sensible definition of `putAll(Map)` in terms of `put(Object, Object)`.
`protected V`	`standardRemove(Object key)` A sensible, albeit inefficient, definition of `remove(java.lang.Object)` in terms of the `iterator` method of `entrySet()`.
`protected String`	`standardToString()` A sensible definition of `ForwardingObject.toString()` in terms of the `iterator` method of `entrySet()`.
`Collection<V>`	`values()`

Methods inherited from class com.google.common.collect.ForwardingObject
toString

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

- Constructor Detail
  - ForwardingMap
```
protected ForwardingMap()
```
    Constructor for use by subclasses.
- Method Detail
  - delegate
```
protected abstract Map<K,V> delegate()
```
    Description copied from class: ForwardingObject
    
    Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.
    
    Specified by:
    
    delegate in class ForwardingObject
  - size
```
public int size()
```
    Specified by:
    
    size in interface Map<K,V>
  - isEmpty
```
public boolean isEmpty()
```
    Specified by:
    
    isEmpty in interface Map<K,V>
  - remove
```
public V remove(Object object)
```
    Specified by:
    
    remove in interface Map<K,V>
  - clear
```
public void clear()
```
    Specified by:
    
    clear in interface Map<K,V>
  - containsKey
```
public boolean containsKey(@Nullable
                  Object key)
```
    Specified by:
    
    containsKey in interface Map<K,V>
  - containsValue
```
public boolean containsValue(@Nullable
                    Object value)
```
    Specified by:
    
    containsValue in interface Map<K,V>
  - get
```
public V get(@Nullable
    Object key)
```
    Specified by:
    
    get in interface Map<K,V>
  - put
```
public V put(K key,
    V value)
```
    Specified by:
    
    put in interface Map<K,V>
  - putAll
```
public void putAll(Map<? extends K,? extends V> map)
```
    Specified by:
    
    putAll in interface Map<K,V>
  - keySet
```
public Set<K> keySet()
```
    Specified by:
    
    keySet in interface Map<K,V>
  - values
```
public Collection<V> values()
```
    Specified by:
    
    values in interface Map<K,V>
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    Specified by:
    
    entrySet in interface Map<K,V>
  - equals
```
public boolean equals(@Nullable
             Object object)
```
    Specified by:
    
    equals in interface Map<K,V>
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface Map<K,V>
    
    Overrides:
    
    hashCode in class Object
  - standardPutAll
```
protected void standardPutAll(Map<? extends K,? extends V> map)
```
    A sensible definition of putAll(Map) in terms of put(Object, Object). If you override put(Object, Object), you may wish to override putAll(Map) to forward to this implementation.
    
    Since:
    
    7.0
  - standardRemove
```
@Beta
protected V standardRemove(@Nullable
                    Object key)
```
    A sensible, albeit inefficient, definition of remove(java.lang.Object) in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override remove(java.lang.Object) to forward to this implementation.
    Alternately, you may wish to override remove(java.lang.Object) with keySet().remove, assuming that approach would not lead to an infinite loop.
    
    Since:
    
    7.0
  - standardClear
```
protected void standardClear()
```
    A sensible definition of clear() in terms of the iterator method of entrySet(). In many cases, you may wish to override clear() to forward to this implementation.
    
    Since:
    
    7.0
  - standardContainsKey
```
@Beta
protected boolean standardContainsKey(@Nullable
                               Object key)
```
    A sensible, albeit inefficient, definition of containsKey(java.lang.Object) in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override containsKey(java.lang.Object) to forward to this implementation.
    
    Since:
    
    7.0
  - standardContainsValue
```
protected boolean standardContainsValue(@Nullable
                            Object value)
```
    A sensible definition of containsValue(java.lang.Object) in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override containsValue(java.lang.Object) to forward to this implementation.
    
    Since:
    
    7.0
  - standardIsEmpty
```
protected boolean standardIsEmpty()
```
    A sensible definition of isEmpty() in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override isEmpty() to forward to this implementation.
    
    Since:
    
    7.0
  - standardEquals
```
protected boolean standardEquals(@Nullable
                     Object object)
```
    A sensible definition of equals(java.lang.Object) in terms of the equals method of entrySet(). If you override entrySet(), you may wish to override equals(java.lang.Object) to forward to this implementation.
    
    Since:
    
    7.0
  - standardHashCode
```
protected int standardHashCode()
```
    A sensible definition of hashCode() in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override hashCode() to forward to this implementation.
    
    Since:
    
    7.0
  - standardToString
```
protected String standardToString()
```
    A sensible definition of ForwardingObject.toString() in terms of the iterator method of entrySet(). If you override entrySet(), you may wish to override ForwardingObject.toString() to forward to this implementation.
    
    Since:
    
    7.0

Class ForwardingMap<K,V>

Nested Class Summary

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

Constructor Summary

Method Summary

Methods inherited from class com.google.common.collect.ForwardingObject

Methods inherited from class java.lang.Object

Constructor Detail

ForwardingMap

Method Detail

delegate

size

isEmpty

remove

clear

containsKey

containsValue

get

put

putAll

keySet

values

entrySet

equals

hashCode

standardPutAll

standardRemove

standardClear

standardContainsKey

standardContainsValue

standardIsEmpty

standardEquals

standardHashCode

standardToString