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package javax.faces.webapp;
import java.util.
Collection;
import java.util.
List;
import java.util.
Map;
import java.util.
Set;
class
TypedCollections {
/**
* Dynamically check that the members of the collection are all
* instances of the given type (or null).
*/
private static boolean
checkCollectionMembers(
Collection<?>
c,
Class<?>
type) {
for (
Object element :
c) {
if (
element != null && !
type.
isInstance(
element)) {
return false;
}
}
return true;
}
/**
* Dynamically check that the members of the collection are all
* instances of the given type (or null), and that the collection
* itself is of the given collection type.
*
* @param <E>
* the collection's element type
* @param c
* the collection to cast
* @param type
* the class of the collection's element type.
* @return the dynamically-type checked collection.
* @throws java.lang.ClassCastException
*/
@
SuppressWarnings("unchecked")
static <E,TypedC extends
Collection<E>> TypedC
dynamicallyCastCollection(
Collection<?>
c,
Class<E>
type,
Class<TypedC>
collectionType) {
if (
c == null)
return null;
if (!
collectionType.
isInstance(
c))
throw new
ClassCastException(
c.
getClass().
getName());
assert
checkCollectionMembers(
c,
type) :
"The collection contains members with a type other than " +
type.
getName();
return
collectionType.
cast(
c);
}
/**
* Dynamically check that the members of the list are all instances of
* the given type (or null).
*
* @param <E>
* the list's element type
* @param list
* the list to cast
* @param type
* the class of the list's element type.
* @return the dynamically-type checked list.
* @throws java.lang.ClassCastException
*/
@
SuppressWarnings("unchecked")
static <E>
List<E>
dynamicallyCastList(
List<?>
list,
Class<E>
type) {
return
dynamicallyCastCollection(
list,
type,
List.class);
}
/**
* Dynamically check that the members of the set are all instances of
* the given type (or null).
*
* @param <E>
* the set's element type
* @param set
* the set to cast
* @param type
* the class of the set's element type.
* @return the dynamically-type checked set.
* @throws java.lang.ClassCastException
*/
@
SuppressWarnings("unchecked")
static <E>
Set<E>
dynamicallyCastSet(
Set<?>
set,
Class<E>
type) {
return
dynamicallyCastCollection(
set,
type,
Set.class);
}
/**
* Dynamically check that the keys and values in the map are all
* instances of the correct types (or null).
*
* @param <K>
* the map's key type
* @param <V>
* the map's value type
* @param map
* the map to cast
* @param keyType
* the class of the map's key type.
* @param valueType
* the class of the map's value type.
* @return the dynamically-type checked map.
* @throws java.lang.ClassCastException
*/
@
SuppressWarnings("unchecked")
static <K, V>
Map<K, V>
dynamicallyCastMap(
Map<?, ?>
map,
Class<K>
keyType,
Class<V>
valueType) {
if (
map == null) {
return null;
}
assert
checkCollectionMembers(
map.
keySet(),
keyType) :
"The map contains keys with a type other than " +
keyType.
getName();
assert
checkCollectionMembers(
map.
values(),
valueType) :
"The map contains values with a type other than " +
valueType.
getName();
return (
Map<K, V>)
map;
}
}