common
Interface MapDiff

All Superinterfaces:

java.util.Map

All Known Implementing Classes:

HashMapDiff, MapWithPreimagesDiff

public interface MapDiff
extends java.util.Map

A map that is represented as a set of changes to some underlying map. A MapDiff object can be modified, but changes to the MapDiff do not affect the underlying map unless changeUnderlyingMap is called. The advantages of using a MapDiff rather than creating another Map object are:

• We do not need to copy the underlying map, which would take time linear in the size of the map.
• We can enumerate the changes between the new map (represented by the MapDiff object) and the underlying map using MapDiff methods, without doing an exhaustive comparison which would take time linear in the size of the underlying map.

A MapDiff behaves correctly if entries are placed in the underlying map after the MapDiff is created. It also behaves correctly if entries are removed from the underlying map, as long as those keys have not also been removed from the MapDiff (then they may be double-counted).

Nested Class Summary

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

java.util.Map.Entry<K,V>

Method Summary

void	changeUnderlying() Changes the underlying map so it is equal to this map.
void	clearChanges() Resets this map so it is equal to the underlying map.
java.util.Set	getChangedKeys() Returns the set of keys that map to different values in this map than in the underlying map.

Methods inherited from interface java.util.Map

clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values

Method Detail

getChangedKeys

java.util.Set getChangedKeys()

Returns the set of keys that map to different values in this map than in the underlying map. This includes any keys that have values in this map but not the underlying map, or vice versa.

The returned set may or may not be kept up to date as changes are made to this MapDiff.

Returns:

unmodifiable Set of Object

changeUnderlying

void changeUnderlying()

Changes the underlying map so it is equal to this map.

Throws:

java.lang.UnsupportedOperationException - if the underlying map is not modifiable

clearChanges

void clearChanges()

Resets this map so it is equal to the underlying map.