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AbstractMap.SimpleImmutableEntry (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

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

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

All Implemented Interfaces:

Serializable, Map.Entry<K,V>

Enclosing class:

AbstractMap<K,V>

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

An Entry maintaining an immutable key and value. This class does not support method setValue. This class may be convenient in methods that return thread-safe snapshots of key-value mappings.

Since:

1.6

See Also:

Serialized Form

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

 

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 (optional operation).
String	toString()           Returns a String representation of this map entry.

 

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

 

Constructor Detail

AbstractMap.SimpleImmutableEntry

public AbstractMap.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

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AbstractMap.SimpleImmutableEntry

public AbstractMap.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 Detail

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

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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

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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 immutable map entry.

Specified by:

setValue in interface Map.Entry<K,V>

Parameters:

value - new value to be stored in this entry

Returns:

(Does not return)

Throws:

UnsupportedOperationException - always

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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()

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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)

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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

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