org.apache.commons.collections
Class BagUtils
java.lang.Object
org.apache.commons.collections.BagUtils
public class BagUtils
extends java.lang.Object
Provides utility methods and decorators for
Bag
and
SortedBag
instances.
$Revision: 1.20 $ $Date: 2004/04/01 20:12:00 $- Paul Jack
- Stephen Colebourne
- Andrew Freeman
- Matthew Hawthorne
BagUtils() - Instantiation of BagUtils is not intended or required.
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EMPTY_BAG
public static final Bag EMPTY_BAG
An empty unmodifiable bag.
EMPTY_SORTED_BAG
public static final Bag EMPTY_SORTED_BAG
An empty unmodifiable sorted bag.
BagUtils
public BagUtils()
Instantiation of BagUtils is not intended or required.
However, some tools require an instance to operate.
predicatedBag
public static Bag predicatedBag(Bag bag,
Predicate predicate)
Returns a predicated (validating) bag backed by the given bag.
Only objects that pass the test in the given predicate can be added to the bag.
Trying to add an invalid object results in an IllegalArgumentException.
It is important not to use the original bag after invoking this method,
as it is a backdoor for adding invalid objects.
bag
- the bag to predicate, must not be nullpredicate
- the predicate for the bag, must not be null
- a predicated bag backed by the given bag
predicatedSortedBag
public static SortedBag predicatedSortedBag(SortedBag bag,
Predicate predicate)
Returns a predicated (validating) sorted bag backed by the given sorted bag.
Only objects that pass the test in the given predicate can be added to the bag.
Trying to add an invalid object results in an IllegalArgumentException.
It is important not to use the original bag after invoking this method,
as it is a backdoor for adding invalid objects.
bag
- the sorted bag to predicate, must not be nullpredicate
- the predicate for the bag, must not be null
- a predicated bag backed by the given bag
synchronizedBag
public static Bag synchronizedBag(Bag bag)
Returns a synchronized (thread-safe) bag backed by the given bag.
In order to guarantee serial access, it is critical that all
access to the backing bag is accomplished through the returned bag.
It is imperative that the user manually synchronize on the returned
bag when iterating over it:
Bag bag = BagUtils.synchronizedBag(new HashBag());
...
synchronized(bag) {
Iterator i = bag.iterator(); // Must be in synchronized block
while (i.hasNext())
foo(i.next());
}
}
Failure to follow this advice may result in non-deterministic
behavior.
bag
- the bag to synchronize, must not be null
- a synchronized bag backed by that bag
synchronizedSortedBag
public static SortedBag synchronizedSortedBag(SortedBag bag)
Returns a synchronized (thread-safe) sorted bag backed by the given
sorted bag.
In order to guarantee serial access, it is critical that all
access to the backing bag is accomplished through the returned bag.
It is imperative that the user manually synchronize on the returned
bag when iterating over it:
SortedBag bag = BagUtils.synchronizedSortedBag(new TreeBag());
...
synchronized(bag) {
Iterator i = bag.iterator(); // Must be in synchronized block
while (i.hasNext())
foo(i.next());
}
}
Failure to follow this advice may result in non-deterministic
behavior.
bag
- the bag to synchronize, must not be null
- a synchronized bag backed by that bag
transformedBag
public static Bag transformedBag(Bag bag,
Transformer transformer)
Returns a transformed bag backed by the given bag.
Each object is passed through the transformer as it is added to the
Bag. It is important not to use the original bag after invoking this
method, as it is a backdoor for adding untransformed objects.
bag
- the bag to predicate, must not be nulltransformer
- the transformer for the bag, must not be null
- a transformed bag backed by the given bag
transformedSortedBag
public static SortedBag transformedSortedBag(SortedBag bag,
Transformer transformer)
Returns a transformed sorted bag backed by the given bag.
Each object is passed through the transformer as it is added to the
Bag. It is important not to use the original bag after invoking this
method, as it is a backdoor for adding untransformed objects.
bag
- the bag to predicate, must not be nulltransformer
- the transformer for the bag, must not be null
- a transformed bag backed by the given bag
typedBag
public static Bag typedBag(Bag bag,
Class type)
Returns a typed bag backed by the given bag.
Only objects of the specified type can be added to the bag.
bag
- the bag to limit to a specific type, must not be nulltype
- the type of objects which may be added to the bag
- a typed bag backed by the specified bag
typedSortedBag
public static SortedBag typedSortedBag(SortedBag bag,
Class type)
Returns a typed sorted bag backed by the given bag.
Only objects of the specified type can be added to the bag.
bag
- the bag to limit to a specific type, must not be nulltype
- the type of objects which may be added to the bag
- a typed bag backed by the specified bag
unmodifiableBag
public static Bag unmodifiableBag(Bag bag)
Returns an unmodifiable view of the given bag. Any modification
attempts to the returned bag will raise an
UnsupportedOperationException
.
bag
- the bag whose unmodifiable view is to be returned, must not be null
- an unmodifiable view of that bag
unmodifiableSortedBag
public static SortedBag unmodifiableSortedBag(SortedBag bag)
Returns an unmodifiable view of the given sorted bag. Any modification
attempts to the returned bag will raise an
UnsupportedOperationException
.
bag
- the bag whose unmodifiable view is to be returned, must not be null
- an unmodifiable view of that bag
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