transformedpredicate.java

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/*
 *  Copyright 2001-2004 The Apache Software Foundation
 *
 *  Licensed 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.functors;

import java.io.Serializable;

import org.apache.commons.collections.Predicate;
import org.apache.commons.collections.Transformer;

/**
 * Predicate implementation that transforms the given object before invoking
 * another <code>Predicate</code>.
 * 
 * @since Commons Collections 3.1
 * @version $Revision: 1.4 $ $Date: 2004/05/31 16:43:17 $
 * @author Alban Peignier
 * @author Stephen Colebourne
 */
public final class TransformedPredicate implements Predicate, PredicateDecorator, Serializable {

    /** Serial version UID */
    static final long serialVersionUID = -5596090919668315834L;
    
    /** The transformer to call */
    private final Transformer iTransformer;
    /** The predicate to call */
    private final Predicate iPredicate;

    /**
     * Factory to create the predicate.
     * 
     * @param transformer  the transformer to call
     * @param predicate  the predicate to call with the result of the transform
     * @return the predicate
     * @throws IllegalArgumentException if the transformer or the predicate is null
     */
    public static Predicate getInstance(Transformer transformer, Predicate predicate) {
        if (transformer == null) {
            throw new IllegalArgumentException("The transformer to call must not be null");
        }
        if (predicate == null) {
            throw new IllegalArgumentException("The predicate to call must not be null");
        }
        return new TransformedPredicate(transformer, predicate);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * 
     * @param transformer  the transformer to use
     * @param predicate  the predicate to decorate
     */
    public TransformedPredicate(Transformer transformer, Predicate predicate) {
        iTransformer = transformer;
        iPredicate = predicate;
    }
    
    /**
     * Evaluates the predicate returning the result of the decorated predicate
     * once the input has been transformed
     * 
     * @param object  the input object which will be transformed
     * @return true if decorated predicate returns true
     */
    public boolean evaluate(Object object) {
        Object result = iTransformer.transform(object);
        return iPredicate.evaluate(result);
    }

    /**
     * Gets the predicate being decorated.
     * 
     * @return the predicate as the only element in an array
     * @since Commons Collections 3.1
     */
    public Predicate[] getPredicates() {
        return new Predicate[] {iPredicate};
    }

    /**
     * Gets the transformer in use.
     * 
     * @return the transformer
     */
    public Transformer getTransformer() {
        return iTransformer;
    }

}