org.apache.commons.collections.collection

Class PredicatedCollection

public class PredicatedCollection extends AbstractSerializableCollectionDecorator

Decorates another Collection to validate that additions match a specified predicate.

This collection exists to provide validation for the decorated collection. It is normally created to decorate an empty collection. If an object cannot be added to the collection, an IllegalArgumentException is thrown.

One usage would be to ensure that no null entries are added to the collection.

Collection coll = PredicatedCollection.decorate(new ArrayList(), NotNullPredicate.INSTANCE);

This class is Serializable from Commons Collections 3.1.

Since: Commons Collections 3.0

Version: $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $

Author: Stephen Colebourne Paul Jack

Field Summary
protected Predicatepredicate
The predicate to use
Constructor Summary
protected PredicatedCollection(Collection coll, Predicate predicate)
Constructor that wraps (not copies).
Method Summary
booleanadd(Object object)
Override to validate the object being added to ensure it matches the predicate.
booleanaddAll(Collection coll)
Override to validate the objects being added to ensure they match the predicate.
static Collectiondecorate(Collection coll, Predicate predicate)
Factory method to create a predicated (validating) collection.
protected voidvalidate(Object object)
Validates the object being added to ensure it matches the predicate.

Field Detail

predicate

protected final Predicate predicate
The predicate to use

Constructor Detail

PredicatedCollection

protected PredicatedCollection(Collection coll, Predicate predicate)
Constructor that wraps (not copies).

If there are any elements already in the collection being decorated, they are validated.

Parameters: coll the collection to decorate, must not be null predicate the predicate to use for validation, must not be null

Throws: IllegalArgumentException if collection or predicate is null IllegalArgumentException if the collection contains invalid elements

Method Detail

add

public boolean add(Object object)
Override to validate the object being added to ensure it matches the predicate.

Parameters: object the object being added

Returns: the result of adding to the underlying collection

Throws: IllegalArgumentException if the add is invalid

addAll

public boolean addAll(Collection coll)
Override to validate the objects being added to ensure they match the predicate. If any one fails, no update is made to the underlying collection.

Parameters: coll the collection being added

Returns: the result of adding to the underlying collection

Throws: IllegalArgumentException if the add is invalid

decorate

public static Collection decorate(Collection coll, Predicate predicate)
Factory method to create a predicated (validating) collection.

If there are any elements already in the collection being decorated, they are validated.

Parameters: coll the collection to decorate, must not be null predicate the predicate to use for validation, must not be null

Returns: a new predicated collection

Throws: IllegalArgumentException if collection or predicate is null IllegalArgumentException if the collection contains invalid elements

validate

protected void validate(Object object)
Validates the object being added to ensure it matches the predicate.

The predicate itself should not throw an exception, but return false to indicate that the object cannot be added.

Parameters: object the object being added

Throws: IllegalArgumentException if the add is invalid

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