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>
implements Map<K,V>

A Map that is backed by a delegate map that contains suppliers for the values that are called lazily when required. The values returned from the delegate 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.

Note: even though this class is effectively immutable and does not support direct mutation, the caching strategy 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.

Nested Class Summary

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

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

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

Map.Entry<K,V>

Method Summary

boolean	containsKey(Object key)
Set<Map.Entry<K,V>>	entrySet()
V	get(Object key) .
boolean	isEmpty()
Set<K>	keySet()
static <K,V> LazyMap<K,V>	newInstance(Map<K,? extends com.google.common.base.Supplier<? extends V>> delegate)
V	remove(Object key)
int	size()

Methods inherited from class java.util.AbstractMap

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

clear, containsValue, equals, hashCode, put, putAll, values

Method Detail

newInstance

public static <K,V> LazyMap<K,V> newInstance(Map<K,? extends com.google.common.base.Supplier<? extends V>> delegate)

get

public V get(Object key)

.

Implements the local caching of a value from the master.

Specified by:

get in interface Map<K,V>

Overrides:

get in class AbstractMap<K,V>

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>