java8.util

Class Maps.Entry

java.lang.Object

java8.util.Maps.Entry

Enclosing class:

Maps

public static final class Maps.Entry
extends Object

A place for the static interface methods of the Java 8 Map.Entry interface.

Method Summary

Modifier and Type	Method and Description
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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

comparingByKey

public 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

public 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

public 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

public 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

public 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 Maps::entry method.

API Note:
An instance obtained from a map's entry-set view has a connection to that map. The copyOf method may be used to create a Map.Entry instance, containing the same key and value, that is independent of any map.

Implementation Note: If the given entry was obtained from a call to copyOf or Maps::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:

17