Package com.atlassian.confluence.util.collections

Class LazyMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

com.atlassian.confluence.util.collections.LazyMap<K,V>

Type Parameters:

K - the key type.

V - the value type.

All Implemented Interfaces:

Map<K,V>

@NotThreadSafe
public class LazyMap<K,V>
extends AbstractMap<K,V>

A Map that is constructed from a map of suppliers for the values, that are evaluated lazily when required. The values returned from the suppliers are cached so they are only retrieved once.

The goal is to reduce the overhead required to instantiate and store entries which might not be used. For example, when rendering Velocity templates, the context map is populated with many things that are only ever required occasionally.

Use copyOf(com.atlassian.confluence.util.collections.LazyMap<K, V>), putAll(LazyMap) and putAllIfAbsent(com.atlassian.confluence.util.collections.LazyMap<K, V>) when copying or merging LazyMap instances. These methods guarantee that the suppliers will not be invoked unnecessarily and never more than once, even when copied to a new map.

This class is not thread-safe and should not be used if thread-safety is required. Adding thread-safety to this class would be fairly trivial through.

Since:

3.4

Nested Class Summary

Nested classes/interfaces inherited from class java.util.AbstractMap

AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K extends Object,V extends Object>

Constructor Summary

Constructors

Constructor	Description
LazyMap()

Method Summary

Modifier and Type	Method	Description
boolean	containsKey(Object key)
static <K, V> LazyMap<K,V>	copyOf(LazyMap<K,V> map)
Set<Map.Entry<K,V>>	entrySet()
static <K, V> LazyMap<K,V>	fromSuppliersMap(Map<K,? extends Supplier<? extends V>> supplierMap)	As at 9.1.1, the returned map is no longer directly backed by the given map.
V	get(Object key)
boolean	isEmpty()
Set<K>	keySet()
void	lazyPut(K key, Supplier<? extends V> value)
static <K, V> LazyMap<K,V>	newInstance(Map<K,? extends com.google.common.base.Supplier<? extends V>> supplierMap)	Deprecated, for removal: This API element is subject to removal in a future version. since 7.0.1.
V	put(K key, V value)
void	putAll(LazyMap<? extends K,? extends V> other)
void	putAll(Map<? extends K,? extends V> m)
void	putAllIfAbsent(LazyMap<K,V> other)
V	remove(Object key)
int	size()

Methods inherited from class java.util.AbstractMap

clear, clone, containsValue, equals, hashCode, toString, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Details

LazyMap

public LazyMap()

Since:

9.1.1

Method Details

newInstance

@Deprecated(forRemoval=true)
public static <K,
V> LazyMap<K,V> newInstance(Map<K,? extends com.google.common.base.Supplier<? extends V>> supplierMap)

Deprecated, for removal: This API element is subject to removal in a future version.

since 7.0.1. Use fromSuppliersMap(Map)

fromSuppliersMap

public static <K,
V> LazyMap<K,V> fromSuppliersMap(Map<K,? extends Supplier<? extends V>> supplierMap)

As at 9.1.1, the returned map is no longer directly backed by the given map. Use lazyPut(K, java.util.function.Supplier<? extends V>), remove(java.lang.Object) and/or other applicable methods to modify the map.

Since:

7.0.1

copyOf

public static <K,
V> LazyMap<K,V> copyOf(LazyMap<K,V> map)

Since:

9.1.1

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

lazyPut

public void lazyPut(K key,
 Supplier<? extends V> value)

Since:

9.1.1

put

public V put(K key,
 V value)

Specified by:

put in interface Map<K,V>

Overrides:

put in class AbstractMap<K,V>

putAll

public void putAll(Map<? extends K,? extends V> m)

Specified by:

putAll in interface Map<K,V>

Overrides:

putAll in class AbstractMap<K,V>

putAll

public void putAll(LazyMap<? extends K,? extends V> other)

Since:

9.1.1

putAllIfAbsent

public void putAllIfAbsent(LazyMap<K,V> other)

Since:

9.1.1

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

Overrides:

keySet in class AbstractMap<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

Overrides:

containsKey in class AbstractMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

Specified by:

entrySet in class AbstractMap<K,V>

size

public int size()

Specified by:

size in interface Map<K,V>

Overrides:

size in class AbstractMap<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

Overrides:

isEmpty in class AbstractMap<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

Overrides:

remove in class AbstractMap<K,V>