org.stekikun.dolmen.common

Class Maps

java.lang.Object

org.stekikun.dolmen.common.Maps

public abstract class Maps
extends Object

This class contains various utility methods about Maps. I wished I had Guava available!

Author:

Stéphane Lescuyer

Method Summary

Modifier and Type	Method and Description
static <K,V> Map<K,V>	create()
static <K,V> Map<K,V>	empty()
static <K,V> V	get(Map<? super K,V> m, K key) This is a strongly-typed alternative to Map.get(Object), which restricts the type of the given key to a sub-type of the declared key type of the map, and also specifies the returned value can be null.
static <K,V> Map<K,V>	singleton(K k, V v)

Methods inherited from class java.lang.Object

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

Method Detail

empty

public static <K,V> Map<K,V> empty()

Returns:

the empty unmodifiable map

singleton

public static <K,V> Map<K,V> singleton(K k,
                                       V v)

Parameters:

k -

v -

Returns:

the singleton hash map binding k to v

get

public static <K,V> V get(Map<? super K,V> m,
                          K key)

This is a strongly-typed alternative to Map.get(Object), which restricts the type of the given key to a sub-type of the declared key type of the map, and also specifies the returned value can be null. For some reason, the JDT seemed to believe the result of Map.get(Object) was non-null and this was leading to some bogus dead-code warnings.

NB: as of Aug. 5th, 2017, I have added external annotations for some library classes such as Map, so that Map.get(Object) now correctly returns a nullable value. This wrapper remains of interest because of the stronger type constraint on the key though.

Parameters:

m -

key -

Returns:

the element associated to key in m, or null if there is no such element

create

public static <K,V> Map<K,V> create()

Returns:

a frehsly allocated hash-map