AbstractMap.SimpleEntry

AI-generated Key Takeaways

• AbstractMap.SimpleEntry provides a basic implementation of the Map.Entry interface, storing a key-value pair.

• It offers methods to get and set the key and value, and to compare entries for equality.

• SimpleEntry can be used to build custom map implementations or for returning entry arrays.

• It includes constructors to create entries from a key-value pair or by copying an existing entry.

• The class implements Serializable, enabling its instances to be serialized and deserialized.

public static class AbstractMap.SimpleEntry extends Object
implements Entry<K, V> Serializable

An Entry maintaining a key and a value. The value may be changed using the setValue method. This class facilitates the process of building custom map implementations. For example, it may be convenient to return arrays of SimpleEntry instances in method Map.entrySet().toArray.

Public Constructor Summary

	SimpleEntry(K key, V value) Creates an entry representing a mapping from the specified key to the specified value.
	SimpleEntry(Entry<? extends K, ? extends V> entry) Creates an entry representing the same mapping as the specified entry.

Public Method Summary

boolean	equals(Object o) Compares the specified object with this entry for equality.
K	getKey() Returns the key corresponding to this entry.
V	getValue() Returns the value corresponding to this entry.
int	hashCode() Returns the hash code value for this map entry.
V	setValue(V value) Replaces the value corresponding to this entry with the specified value.
String	toString() Returns a String representation of this map entry.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.util.Map.Entry

static <K, V> Comparator<Entry<K, V>>	comparingByKey(Comparator<? super K> cmp) Returns a comparator that compares Map.Entry by key using the given Comparator.
static <K extends Comparable<? super K>, V> Comparator<Entry<K, V>>	comparingByKey() Returns a comparator that compares Map.Entry in natural order on key.
static <K, V> Comparator<Entry<K, V>>	comparingByValue(Comparator<? super V> cmp) Returns a comparator that compares Map.Entry by value using the given Comparator.
static <K, V extends Comparable<? super V>> Comparator<Entry<K, V>>	comparingByValue() Returns a comparator that compares Map.Entry in natural order on value.
abstract boolean	equals(Object o) Compares the specified object with this entry for equality.
abstract K	getKey() Returns the key corresponding to this entry.
abstract V	getValue() Returns the value corresponding to this entry.
abstract int	hashCode() Returns the hash code value for this map entry.
abstract V	setValue(V value) Replaces the value corresponding to this entry with the specified value (optional operation).

Public Constructors

public SimpleEntry (K key, V value)

Creates an entry representing a mapping from the specified key to the specified value.

Parameters

key	the key represented by this entry
value	the value represented by this entry

public SimpleEntry (Entry<? extends K, ? extends V> entry)

Creates an entry representing the same mapping as the specified entry.

Parameters

entry	the entry to copy

Public Methods

public boolean equals (Object o)

Compares the specified object with this entry for equality. Returns true if the given object is also a map entry and the two entries represent the same mapping. More formally, two entries e1 and e2 represent the same mapping if

   (e1.getKey()==null ?
    e2.getKey()==null :
    e1.getKey().equals(e2.getKey()))
   &&
   (e1.getValue()==null ?
    e2.getValue()==null :
    e1.getValue().equals(e2.getValue()))

This ensures that the equals method works properly across different implementations of the Map.Entry interface.

Parameters

o	object to be compared for equality with this map entry

Returns

• true if the specified object is equal to this map entry

See Also

• hashCode()

public K getKey ()

Returns the key corresponding to this entry.

Returns

• the key corresponding to this entry

public V getValue ()

Returns the value corresponding to this entry.

Returns

• the value corresponding to this entry

public int hashCode ()

Returns the hash code value for this map entry. The hash code of a map entry e is defined to be:

   (e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
   (e.getValue()==null ? 0 : e.getValue().hashCode())

This ensures that e1.equals(e2) implies that e1.hashCode()==e2.hashCode() for any two Entries e1 and e2, as required by the general contract of Object.hashCode().

Returns

• the hash code value for this map entry

See Also

• equals(Object)

public V setValue (V value)

Replaces the value corresponding to this entry with the specified value.

Parameters

value	new value to be stored in this entry

Returns

• the old value corresponding to the entry

public String toString ()

Returns a String representation of this map entry. This implementation returns the string representation of this entry's key followed by the equals character ("=") followed by the string representation of this entry's value.

Returns

• a String representation of this map entry