Commons Collections example source code file (TransformerPredicate.java)

This example Commons Collections source code file (TransformerPredicate.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

boolean, boolean, functorexception, illegalargumentexception, io, object, predicate, predicate, serializable, the, transformer, transformer, transformerpredicate, transformerpredicate

The Commons Collections TransformerPredicate.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.functors;

import java.io.Serializable;

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

/**
 * Predicate implementation that returns the result of a transformer.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public final class TransformerPredicate implements Predicate, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -2407966402920578741L;
    
    /** The transformer to call */
    private final Transformer iTransformer;
    
    /**
     * Factory to create the predicate.
     * 
     * @param transformer  the transformer to decorate
     * @return the predicate
     * @throws IllegalArgumentException if the transformer is null
     */
    public static Predicate getInstance(Transformer transformer) {
        if (transformer == null) {
            throw new IllegalArgumentException("The transformer to call must not be null");
        }
        return new TransformerPredicate(transformer);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance if you want that.
     * 
     * @param transformer  the transformer to decorate
     */
    public TransformerPredicate(Transformer transformer) {
        super();
        iTransformer = transformer;
    }

    /**
     * Evaluates the predicate returning the result of the decorated transformer.
     * 
     * @param object  the input object
     * @return true if decorated transformer returns Boolean.TRUE
     * @throws FunctorException if the transformer returns an invalid type
     */
    public boolean evaluate(Object object) {
        Object result = iTransformer.transform(object);
        if (result instanceof Boolean == false) {
            throw new FunctorException(
                "Transformer must return an instanceof Boolean, it was a "
                    + (result == null ? "null object" : result.getClass().getName()));
        }
        return ((Boolean) result).booleanValue();
    }

    /**
     * Gets the transformer.
     * 
     * @return the transformer
     * @since Commons Collections 3.1
     */
    public Transformer getTransformer() {
        return iTransformer;
    }

}