com.google.common.collect
Class ForwardingMapEntry<K,V>

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

All Implemented Interfaces:

Map.Entry<K,V>

@GwtCompatible
public abstract class ForwardingMapEntry<K,V>
extends ForwardingObject
implements Map.Entry<K,V>

A map entry which forwards all its method calls to another map entry. Subclasses should override one or more methods to modify the behavior of the backing map entry as desired per the decorator pattern.

Warning: The methods of ForwardingMapEntry forward indiscriminately to the methods of the delegate. For example, overriding getValue() alone will not change the behavior of equals(java.lang.Object), which can lead to unexpected behavior. In this case, you should override equals as well, either providing your own implementation, or delegating to the provided standardEquals 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 the entry of a SortedMap whose comparator is not consistent with equals.

The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.

Since:

2 (imported from Google Collections Library)

Author:

Mike Bostock, Louis Wasserman

ForwardingMapEntry

protected ForwardingMapEntry()

Constructor for use by subclasses.

delegate

protected abstract Map.Entry<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

getKey

public K getKey()

Description copied from interface: java.util.Map.Entry

Returns the key corresponding to this entry.

Specified by:

getKey in interface Map.Entry<K,V>

Returns:

the key corresponding to this entry

getValue

public V getValue()

Description copied from interface: java.util.Map.Entry

Returns the value corresponding to this entry. If the mapping has been removed from the backing map (by the iterator's remove operation), the results of this call are undefined.

Specified by:

getValue in interface Map.Entry<K,V>

Returns:

the value corresponding to this entry

setValue

public V setValue(V value)

Description copied from interface: java.util.Map.Entry

Replaces the value corresponding to this entry with the specified value (optional operation). (Writes through to the map.) The behavior of this call is undefined if the mapping has already been removed from the map (by the iterator's remove operation).

Specified by:

setValue in interface Map.Entry<K,V>

Parameters:

value - new value to be stored in this entry

Returns:

old value corresponding to the entry

equals

public boolean equals(@Nullable
                      Object object)

Description copied from class: java.lang.Object

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.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specified by:

equals in interface Map.Entry<K,V>

Overrides:

equals in class Object

Parameters:

object - the reference object with which to compare.

Returns:

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

See Also:

Object.hashCode(), Hashtable

hashCode

public int hashCode()

Description copied from class: java.lang.Object

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

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(Object) 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 Object.equals(java.lang.Object) 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 hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java^TM programming language.)

Specified by:

hashCode in interface Map.Entry<K,V>

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), Hashtable

standardEquals

@Beta
protected boolean standardEquals(@Nullable
                                      Object object)

A sensible definition of equals(Object) in terms of getKey() and getValue(). If you override either of these methods, you may wish to override equals(Object) to forward to this implementation.

Since:

7

standardHashCode

@Beta
protected int standardHashCode()

A sensible definition of hashCode() in terms of getKey() and getValue(). If you override either of these methods, you may wish to override hashCode() to forward to this implementation.

Since:

7

standardToString

@Beta
protected String standardToString()

A sensible definition of ForwardingObject.toString() in terms of getKey() and getValue(). If you override either of these methods, you may wish to override equals(java.lang.Object) to forward to this implementation.

Since:

7