io.github.lukehutch.fastclasspathscanner.utils

Class LazyMap<K,V>

java.lang.Object

io.github.lukehutch.fastclasspathscanner.utils.LazyMap<K,V>

public abstract class LazyMap<K,V>
extends Object

Used to wrap a map with lazy evaluation, so work is not done unless it is needed. (e.g. if you don't use the annotations features of the API, most of the annotations data structures are not built.) Either override initialize() if you need to initialize and finalize the entire map at once, or, better, override generateValue() to compute map entries only as they are requested.

Field Summary

Fields

Modifier and Type	Field and Description
protected HashMap<K,V>	map

Constructor Summary

Constructors

Constructor and Description
LazyMap()

Method Summary

Modifier and Type	Method and Description
void	clear() Clear the map.
static <K,V extends Comparable<V>> LazyMap<K,ArrayList<V>>	convertToMultiMapSorted(LazyMap<K,HashSet<V>> lazyMap) Convert a lazy MultiSet into a lazy MultiMap.
void	generateAllValues(Collection<K> keys) Ensure that all keys in the provided collection have been initialized or generated.
protected V	generateValue(K key) Override this to generate a single value each time get() is called.
V	get(K key) Get the requested key.
void	initialize() Override this to initialize the entire map the first time get() is called.
static <K,V,T> LazyMap<V,HashSet<K>>	invertMultiSet(LazyMap<K,HashSet<V>> lazyMap) Invert the map to find the preimage of each unique value.
static <K,V,T> LazyMap<V,HashSet<K>>	invertMultiSet(LazyMap<K,HashSet<V>> lazyMap, LazyMap<K,T> templateLazyMap) For all keys in templateLazyMap, generate the value for each key, then invert the map to find the preimage of each unique value.
Set<K>	keySet() Returns all keys in the map that have been initialized so far.
String	toString()
Collection<V>	values() Returns all values in the map that have been initialized so far.

Methods inherited from class java.lang.Object

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

Field Detail

map

protected final HashMap<K,V> map

Constructor Detail

LazyMap

public LazyMap()

Method Detail

generateValue

protected V generateValue(K key)

Override this to generate a single value each time get() is called. The result will be cached in the map.

initialize

public void initialize()

Override this to initialize the entire map the first time get() is called.

clear

public void clear()

Clear the map.

generateAllValues

public void generateAllValues(Collection<K> keys)

Ensure that all keys in the provided collection have been initialized or generated.

get

public V get(K key)

Get the requested key. If initialize() has not yet been called, it will be called. If the map does not yet contain the key, generateValue(key) will be called, and the result will be stored in the map. If there is still no value corresponding to the key in the map, null will be returned.

values

public Collection<V> values()

Returns all values in the map that have been initialized so far. If the map is not exhaustively initialized in the initialize() method, this will not contain all possible values for the map, only the values that have been computed as a result of calling generateValue().

keySet

public Set<K> keySet()

Returns all keys in the map that have been initialized so far. If the map is not exhaustively initialized in the initialize() method, this will not contain all possible keys for the map, only the keys that have been passed so far to generateValue().

toString

public String toString()

Overrides:

toString in class Object

invertMultiSet

public static <K,V,T> LazyMap<V,HashSet<K>> invertMultiSet(LazyMap<K,HashSet<V>> lazyMap,
                                                           LazyMap<K,T> templateLazyMap)

For all keys in templateLazyMap, generate the value for each key, then invert the map to find the preimage of each unique value. The keySet in templateLazyMap is read the first time get() is called on the returned LazyMap. (i.e. the template is only needed so that even keySet generation happens lazily.)

invertMultiSet

public static <K,V,T> LazyMap<V,HashSet<K>> invertMultiSet(LazyMap<K,HashSet<V>> lazyMap)

Invert the map to find the preimage of each unique value. The LazyMap should be defined by overriding initialize(), not using generateValue().

convertToMultiMapSorted

public static <K,V extends Comparable<V>> LazyMap<K,ArrayList<V>> convertToMultiMapSorted(LazyMap<K,HashSet<V>> lazyMap)

Convert a lazy MultiSet into a lazy MultiMap. Value lists are sorted in the result.