Module java.base

Package java.util

Class AbstractMap.SimpleImmutableEntry<K,V>

java.lang.Object

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

Type Parameters:

K - the type of the keys

V - the type of the value

All Implemented Interfaces:

Serializable, Map.Entry<K,V>

Enclosing class:

AbstractMap<K,V>

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

An unmodifiable Entry maintaining a key and a value. This class does not support the setValue method. Instances of this class are not associated with any map nor with any map's entry-set view.

API Note:

Instances of this class are not necessarily immutable, as the key and value may be mutable. An instance of this specific class is unmodifiable, because the key and value references cannot be changed. A reference of this type may not be unmodifiable, as a subclass may be modifiable or may provide the appearance of modifiability.

This class may be convenient in methods that return thread-safe snapshots of key-value mappings. For alternatives, see the Map::entry and Map.Entry::copyOf methods.

Since:

1.6

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
SimpleImmutableEntry(Map.Entry<? extends K,? extends V> entry)	Creates an entry representing the same mapping as the specified entry.
SimpleImmutableEntry(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 (optional operation).
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

SimpleImmutableEntry

public SimpleImmutableEntry(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

SimpleImmutableEntry

public SimpleImmutableEntry(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 (optional operation). This implementation simply throws UnsupportedOperationException, as this class implements an unmodifiable map entry.

Specified by:

setValue in interface Map.Entry<K,V>

Implementation Requirements:

The implementation in this class always throws UnsupportedOperationException.

Parameters:

value - new value to be stored in this entry

Returns:

(Does not return)

Throws:

UnsupportedOperationException - always

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