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Commons Collections example source code file (PredicatedCollection.java)

This example Commons Collections source code file (PredicatedCollection.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

abstractserializablecollectiondecorator, cannot, collection, illegalargumentexception, illegalargumentexception, iterator, iterator, object, predicate, predicate, predicatedcollection, predicatedcollection, util

The Commons Collections PredicatedCollection.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.collection;

import java.util.Collection;
import java.util.Iterator;

import org.apache.commons.collections.Predicate;

/**
 * Decorates another <code>Collection to validate that additions
 * match a specified predicate.
 * <p>
 * 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.
 * <p>
 * One usage would be to ensure that no null entries are added to the collection.
 * <pre>Collection coll = PredicatedCollection.decorate(new ArrayList(), NotNullPredicate.INSTANCE);
* <p> * This class is Serializable from Commons Collections 3.1. * * @since Commons Collections 3.0 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ * * @author Stephen Colebourne * @author Paul Jack */ public class PredicatedCollection extends AbstractSerializableCollectionDecorator { /** Serialization version */ private static final long serialVersionUID = -5259182142076705162L; /** The predicate to use */ protected final Predicate predicate; /** * Factory method to create a predicated (validating) collection. * <p> * If there are any elements already in the collection being decorated, they * are validated. * * @param coll the collection to decorate, must not be null * @param predicate the predicate to use for validation, must not be null * @return a new predicated collection * @throws IllegalArgumentException if collection or predicate is null * @throws IllegalArgumentException if the collection contains invalid elements */ public static Collection decorate(Collection coll, Predicate predicate) { return new PredicatedCollection(coll, predicate); } //----------------------------------------------------------------------- /** * Constructor that wraps (not copies). * <p> * If there are any elements already in the collection being decorated, they * are validated. * * @param coll the collection to decorate, must not be null * @param predicate the predicate to use for validation, must not be null * @throws IllegalArgumentException if collection or predicate is null * @throws IllegalArgumentException if the collection contains invalid elements */ protected PredicatedCollection(Collection coll, Predicate predicate) { super(coll); if (predicate == null) { throw new IllegalArgumentException("Predicate must not be null"); } this.predicate = predicate; for (Iterator it = coll.iterator(); it.hasNext(); ) { validate(it.next()); } } /** * Validates the object being added to ensure it matches the predicate. * <p> * The predicate itself should not throw an exception, but return false to * indicate that the object cannot be added. * * @param object the object being added * @throws IllegalArgumentException if the add is invalid */ protected void validate(Object object) { if (predicate.evaluate(object) == false) { throw new IllegalArgumentException("Cannot add Object '" + object + "' - Predicate rejected it"); } } //----------------------------------------------------------------------- /** * Override to validate the object being added to ensure it matches * the predicate. * * @param object the object being added * @return the result of adding to the underlying collection * @throws IllegalArgumentException if the add is invalid */ public boolean add(Object object) { validate(object); return getCollection().add(object); } /** * 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. * * @param coll the collection being added * @return the result of adding to the underlying collection * @throws IllegalArgumentException if the add is invalid */ public boolean addAll(Collection coll) { for (Iterator it = coll.iterator(); it.hasNext(); ) { validate(it.next()); } return getCollection().addAll(coll); } }

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