Map.Entry (FlexDoc/Javadoc 2.0 Demo)

A map entry (key-value pair). The Entry may be unmodifiable, or the value may be modifiable if the optional setValue method is implemented. The Entry may be independent of any map, or it may represent an entry of the entry-set view of a map.

Instances of the Map.Entry interface may be obtained by iterating the entry-set view of a map. These instances maintain a connection to the original, backing map. This connection to the backing map is valid only for the duration of iteration over the entry-set view. During iteration of the entry-set view, if supported by the backing map, a change to a Map.Entry's value via the setValue method will be visible in the backing map. The behavior of such a Map.Entry instance is undefined outside of iteration of the map's entry-set view. It is also undefined if the backing map has been modified after the Map.Entry was returned by the iterator, except through the Map.Entry.setValue method. In particular, a change to the value of a mapping in the backing map might or might not be visible in the corresponding Map.Entry element of the entry-set view.

Since:

1.2

See Also:

Map.entrySet()

Method Summary
static <K extends Comparable<? super K>,V> Comparator<Map.Entry<K,V>>	comparingByKey() Returns a comparator that compares Map.Entry in natural order on key.
static <K,V> Comparator<Map.Entry<K,V>>	comparingByKey(Comparator<? super K> cmp) Returns a comparator that compares Map.Entry by key using the given Comparator.
static <K,V extends Comparable<? super V>> Comparator<Map.Entry<K,V>>	comparingByValue() Returns a comparator that compares Map.Entry in natural order on value.
static <K,V> Comparator<Map.Entry<K,V>>	comparingByValue(Comparator<? super V> cmp) Returns a comparator that compares Map.Entry by value using the given Comparator.
static <K,V> Map.Entry<K,V>	copyOf(Map.Entry<? extends K,? extends V> e) Returns a copy of the given Map.Entry.
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).

Method Detail

getKey

K getKey

()

Returns the key corresponding to this entry.

Returns:

the key corresponding to this entry

Throws:

IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.

getValue

V getValue

()

Returns the value corresponding to this entry. If the mapping has been removed from the backing map (by the iterator's remove operation), the results of this call are undefined.

Returns:

the value corresponding to this entry

Throws:

IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.

setValue

V setValue

(V value)

Replaces the value corresponding to this entry with the specified value (optional operation). (Writes through to the map.) The behavior of this call is undefined if the mapping has already been removed from the map (by the iterator's remove operation).

Parameters:

value - new value to be stored in this entry

Returns:

old value corresponding to the entry

Throws:

UnsupportedOperationException - if the put operation is not supported by the backing map

ClassCastException - if the class of the specified value prevents it from being stored in the backing map

NullPointerException - if the backing map does not permit null values, and the specified value is null

IllegalArgumentException - if some property of this value prevents it from being stored in the backing map

IllegalStateException - implementations may, but are not required to, throw this exception if the entry has been removed from the backing map.

equals

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.

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:

Object.hashCode(), HashMap

hashCode

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.

Overrides:

hashCode in class Object

Returns:

the hash code value for this map entry

comparingByKey

static <K extends Comparable<? super K>,V> Comparator<Map.Entry<K,V>> comparingByKey

()

Returns a comparator that compares Map.Entry in natural order on key.

The returned comparator is serializable and throws NullPointerException when comparing an entry with a null key.

Type Parameters:

K - the Comparable type of then map keys

V - the type of the map values

Returns:

a comparator that compares Map.Entry in natural order on key.

Since:

1.8

See Also:

Comparable

comparingByValue

static <K,V extends Comparable<? super V>> Comparator<Map.Entry<K,V>> comparingByValue

()

Returns a comparator that compares Map.Entry in natural order on value.

The returned comparator is serializable and throws NullPointerException when comparing an entry with null values.

Type Parameters:

K - the type of the map keys

V - the Comparable type of the map values

Returns:

a comparator that compares Map.Entry in natural order on value.

Since:

1.8

See Also:

Comparable

comparingByKey

static <K,V> Comparator<Map.Entry<K,V>> comparingByKey

(Comparator<? super K> cmp)

Returns a comparator that compares Map.Entry by key using the given Comparator.

The returned comparator is serializable if the specified comparator is also serializable.

Type Parameters:

K - the type of the map keys

V - the type of the map values

Parameters:

cmp - the key Comparator

Returns:

a comparator that compares Map.Entry by the key.

Since:

1.8

comparingByValue

static <K,V> Comparator<Map.Entry<K,V>> comparingByValue

(Comparator<? super V> cmp)

Returns a comparator that compares Map.Entry by value using the given Comparator.

The returned comparator is serializable if the specified comparator is also serializable.

Type Parameters:

K - the type of the map keys

V - the type of the map values

Parameters:

cmp - the value Comparator

Returns:

a comparator that compares Map.Entry by the value.

Since:

1.8

copyOf

static <K,V> Map.Entry<K,V> copyOf

(Map.Entry<? extends K,? extends V> e)

Returns a copy of the given Map.Entry. The returned instance is not associated with any map. The returned instance has the same characteristics as instances returned by the Map::entry method.

Implementation Note:

If the given entry was obtained from a call to copyOf or Map::entry, calling copyOf will generally not create another copy.

Type Parameters:

K - the type of the key

V - the type of the value

Parameters:

e - the entry to be copied

Returns:

a map entry equal to the given entry

Throws:

NullPointerException - if e is null or if either of its key or value is null

Since:

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