Package uk.ac.starlink.util
Class MapGroup<K,V>
java.lang.Object
uk.ac.starlink.util.MapGroup<K,V>
Represents an ordered list of
Map
s containing
related data.
The same keys may crop up in the maps comprising the groups, and
are taken to have the same meaning, so that all the values associated
with a given key in any of the maps in the group are taken to be
a related set. There is no requirement however that a key which
appears in one of the maps has to appear in any or all of the others.
A single list of the union of all the keys which appear in any
of the maps in the group can be obtained. An ordering may be
imposed on this list.- Author:
- Mark Taylor (Starlink)
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
Adds a new Map to the end of this group.Returns the list which defines ordering for any keys which crop up.Returns a list of all the keys which appear in any of the metadata sets.getMaps()
Returns an unmodifiable list of all the maps in this group.void
Removes all entries with a given key for every map in this group.void
removeKeys
(Collection<K> keys) Removes all entries which have a key in a given collection for every map in this group.void
retainKeys
(Collection<K> keys) Removes all entries except those with keys in a given collection for every map in this group.void
setKeyOrder
(List<K> ordering) Mandates an ordering to be imposed on the map keys.void
setKnownKeys
(List<K> keys) Sets the list of known keys.int
size()
Returns the number of maps in this group.
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Constructor Details
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MapGroup
public MapGroup()Constructs a newMapGroup
.
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Method Details
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addMap
Adds a new Map to the end of this group.- Parameters:
map
- the map to add
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getMaps
Returns an unmodifiable list of all the maps in this group. It is unmodifiable so that you can't put anything in it which is not aMap
.- Returns:
- a list of the maps
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size
public int size()Returns the number of maps in this group.- Returns:
- map count
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setKeyOrder
Mandates an ordering to be imposed on the map keys. The effect of this call is to influence the order of the list returned by subsequent calls ofgetKnownKeys()
.The supplied argument
ordering
is a list of objects; an object which appears earlier in this list is considered to be earlier in the list ofMapGroup
keys. Any which do not appear in this list will be ranked in an unspecified order at the end (their natural comparison order will be used if both objects implementComparable
).- Parameters:
ordering
- a list of objects which may appear in this group's map keys
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getKeyOrder
Returns the list which defines ordering for any keys which crop up.- Returns:
- current key ordering
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removeKeys
Removes all entries which have a key in a given collection for every map in this group.- Parameters:
keys
- the set of key values whose entries must be removed
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removeKey
Removes all entries with a given key for every map in this group.- Parameters:
key
- the key whose entries must be removed
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retainKeys
Removes all entries except those with keys in a given collection for every map in this group.- Parameters:
keys
- the keys whose entries must be retained
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setKnownKeys
Sets the list of known keys. This list, if not null, will be returned by subsequent calls ofgetKnownKeys()
.- Parameters:
keys
- collection of keys
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getKnownKeys
Returns a list of all the keys which appear in any of the metadata sets. The order is determined by the most recent call ofsetKeyOrder(java.util.List<K>)
. If it has never been called they will be returned in an arbitrary order. IfsetKnownKeys(java.util.List<K>)
has been called with a non-null argument, that list will be returned instead.- Returns:
- the list of map keys
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