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

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

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

All Implemented Interfaces:

Serializable, Map.Entry<K,V>

Enclosing class:

AbstractMap<K,V>

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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. 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

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Constructor Summary
AbstractMap.SimpleEntry(K key, V value)           Creates an entry representing a mapping from the specified key to the specified value.
AbstractMap.SimpleEntry(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.
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.SimpleEntry

public AbstractMap.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

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AbstractMap.SimpleEntry

public AbstractMap.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 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.

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

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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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