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public interface FeatureCollection<T extends FeatureType,F extends Feature>
Represents a collection of features.
Implementations (and client code) should adhere to the rules set forth by java.util.Collection. That is, some methods are optional to implement, and may throw an UnsupportedOperationException.
FeatureCollection
In programmer speak a FeatureCollection
We have also adopted an additional constraint on the use of iterator. You must call FeatureCollection.close( iterator ) to allow FeatureCollection to clean up any operating system resources used to acces information.
Example (safe) use:
Iterator iterator = collection.iterator();
try {
for( Iterator i=collection.iterator(); i.hasNext();){
Feature feature = (Feature) i.hasNext();
System.out.println( feature.getID() );
}
}
finally {
collection.close( iterator );
}
Handy Tip: Although many resource backed collections will choose to release resources at when the iterator has reached the end of its contents this is not something you should rely on.
Many users will be treating this as a straight forward Collection, there code will break often enough due to latency - try and close up resources for them when you can detect that an Iterator is not useful anymore.
Collections are used in two fashions, basically as you see them, and also as "range" for common opperations. You can see this with List.subCollection( Filter ). Existing RnD effort is going towards supporting this kind of use at the FeatureCollection level.
java.util.Collection, org.geotools.Feature
Method Summary | ||
---|---|---|
void |
accepts(FeatureVisitor visitor,
ProgressListener progress)
Visit the contents of a feature collection. |
|
boolean |
add(F obj)
Add object to this collection. |
|
boolean |
addAll(Collection<? extends F> collection)
Add all the objects to the collection. |
|
boolean |
addAll(FeatureCollection<? extends T,? extends F> resource)
|
|
void |
addListener(CollectionListener listener)
Adds a listener for collection events. |
|
void |
clear()
|
|
void |
close(FeatureIterator<F> close)
Clean up after any resources associated with this FeatureIterator in a manner similar to JDO collections. |
|
void |
close(Iterator<F> close)
Clean up after any resources associated with this itterator in a manner similar to JDO collections. |
|
boolean |
contains(Object o)
|
|
boolean |
containsAll(Collection<?> o)
|
|
FeatureIterator<F> |
features()
Obtain a FeatureIterator |
|
ReferencedEnvelope |
getBounds()
Get the total bounds of this collection which is calculated by doing a union of the bounds of each feature inside of it |
|
String |
getID()
ID used when serializing to GML |
|
T |
getSchema()
The schema for the child features of this collection. |
|
boolean |
isEmpty()
|
|
Iterator<F> |
iterator()
An iterator over this collection, which must be closed after use. |
|
void |
purge()
Deprecated. No longer needed as iterator use by java for each construct not available |
|
boolean |
remove(Object o)
|
|
boolean |
removeAll(Collection<?> c)
|
|
void |
removeListener(CollectionListener listener)
Removes a listener for collection events. |
|
boolean |
retainAll(Collection<?> c)
|
|
int |
size()
|
|
FeatureCollection<T,F> |
sort(SortBy order)
collection.subCollection( myFilter ).sort( {"foo","bar"} ); collection.subCollection( myFilter ).sort( "bar" ).sort("foo") |
|
FeatureCollection<T,F> |
subCollection(Filter filter)
FeatureCollection |
|
Object[] |
toArray()
|
|
|
toArray(O[] a)
|
Method Detail |
---|
FeatureIterator<F> features()
The implementation of Collection must adhere to the rules of
fail-fast concurrent modification. In addition (to allow for
resource backed collections, the close( Iterator )
method must be called.
This is almost equivalent to:
getAttribute(getFeatureType().getAttributeType(0).getName()).iterator();
.
Iterator<Feature>
FeatureIterator iterator=collection.features();
try {
while( iterator.hasNext() ){
Feature feature = iterator.next();
System.out.println( feature.getID() );
}
}
finally {
collection.close( iterator );
}
GML Note: The contents of this iterator are considered to be defined by featureMember tags (and/or the single allowed FeatureMembers tag). Please see getFeatureType for more details.
void close(FeatureIterator<F> close)
Iterator iterator = collection.iterator();
try {
for( Iterator i=collection.iterator(); i.hasNext();){
Feature feature = i.hasNext();
System.out.println( feature.getID() );
}
}
finally {
collection.close( iterator );
}
close
- void close(Iterator<F> close)
Iterator iterator = collection.iterator();
try {
for( Iterator i=collection.iterator(); i.hasNext();){
Feature feature = (Feature) i.hasNext();
System.out.println( feature.getID() );
}
}
finally {
collection.close( iterator );
}
close
- void addListener(CollectionListener listener) throws NullPointerException
When this collection is backed by live data the event notification will follow the guidelines outlined by FeatureListner.
listener
- The listener to add
NullPointerException
- If the listener is null.void removeListener(CollectionListener listener) throws NullPointerException
listener
- The listener to remove
NullPointerException
- If the listener is null.T getSchema()
There is a difference between getFeatureType() and getSchema()represents the LCD FeatureType that best represents the contents of this collection.
The method getSchema() is named for compatability with the geotools 2.0 API. In the Geotools 2.2 time frame we should be able to replace this method with a careful check of getFeatureType() and its attributes.
String getID()
void accepts(FeatureVisitor visitor, ProgressListener progress) throws IOException
The order of traversal is dependent on the FeatureCollection implementation; some collections are able to make efficient use of an internal index in order to quickly visit features located in the same region.
visitor
- Closure applied to each feature in turn.progress
- Used to report progress, may be used to interrupt the operation
IOException
FeatureCollection<T,F> subCollection(Filter filter)
The contents of the returned FeatureCollection
This method is used cut down on the number of filter based methods
required for a useful FeatureCollection
Example Use:
The results of subCollection:
The above recommended use is agreement with the Collections API precident of
List.subList( start, end ).
collection.subCollection( filter ).clear();
filter
-
FeatureList
FeatureCollection<T,F> sort(SortBy order)
order
-
ReferencedEnvelope getBounds()
Iterator<F> iterator()
Collection is not guaranteed to be ordered in any manner.
The implementation of Collection must adhere to the rules of
fail-fast concurrent modification. In addition (to allow for
resource backed collections, the close( Iterator )
method must be called.
Example (safe) use:
Iterator iterator = collection.iterator();
try {
while( iterator.hasNext();){
Feature feature = (Feature) iterator.hasNext();
System.out.println( feature.getID() );
}
}
finally {
collection.close( iterator );
}
void purge()
This method should be used with great caution, it is however available to allow the use of the ResourceCollection with algorthims that are unaware of the need to close iterators after use.
Example of using a normal Collections utility method:
Collections.sort( collection );
collection.purge();
boolean add(F obj)
This method is often not impelmented for collections produced as the result of a query.
Collection.add(Object)
boolean addAll(Collection<? extends F> collection)
This method is often not implemented for collections produced as the results of a query.
Collection.addAll(Collection)
boolean addAll(FeatureCollection<? extends T,? extends F> resource)
addAll(Collection)
void clear()
Collection.clear()
boolean contains(Object o)
Collection.contains(Object)
boolean containsAll(Collection<?> o)
Collection.containsAll(Collection)
boolean isEmpty()
Collection.isEmpty()
boolean remove(Object o)
Collection.remove(Object)
boolean removeAll(Collection<?> c)
Collection.removeAll(Collection)
boolean retainAll(Collection<?> c)
Collection.retainAll(Collection)
int size()
Collection.size()
Object[] toArray()
Collection.toArray()
<O> O[] toArray(O[] a)
Collection.toArray(Object[])
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