Module java.base

Package java.util

Class AbstractMap.SimpleEntry<K,V>

java.lang.Object

java.util.AbstractMap.SimpleEntry<K,V>

Type Parameters:

K - the type of key

V - the type of the value

All Implemented Interfaces:

Serializable, Map.Entry<K,V>

Enclosing class:

AbstractMap<K,V>

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

An Entry maintaining a key and a value. The value may be changed using the setValue method. Instances of this class are not associated with any map nor with any map's entry-set view.

API Note:

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.

Since:

1.6

See Also:

• Serialized Form

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
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.

Methods declared in class java.lang.Object

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

Constructor Details

SimpleEntry

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

SimpleEntry

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

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

Parameters:

entry - the entry to copy

Method Details

getKey

public K getKey()

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()

Returns the value corresponding to this entry.

Specified by:

getValue in interface Map.Entry<K,V>

Returns:

the value corresponding to this entry

setValue

public V setValue(V value)

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

Specified by:

setValue in interface Map.Entry<K,V>

Parameters:

value - new value to be stored in this entry

Returns:

the old value corresponding to the entry

equals

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.

Specified by:

equals in interface Map.Entry<K,V>

Overrides:

equals in class Object

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()

hashCode

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().

Specified by:

hashCode in interface Map.Entry<K,V>

Overrides:

hashCode in class Object

Returns:

the hash code value for this map entry

See Also:

• equals(java.lang.Object)

toString

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.

Overrides:

toString in class Object

Returns:

a String representation of this map entry