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Commons Collections example source code file (NullIsFalsePredicate.java)

This example Commons Collections source code file (NullIsFalsePredicate.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

illegalargumentexception, io, nullisfalsepredicate, nullisfalsepredicate, predicate, predicate, predicatedecorator, predicatedecorator, serializable, serializable

The Commons Collections NullIsFalsePredicate.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.Predicate;

/**
 * Predicate implementation that returns false if the input is null.
 * 
 * @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 NullIsFalsePredicate implements Predicate, PredicateDecorator, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -2997501534564735525L;
    
    /** The predicate to decorate */
    private final Predicate iPredicate;
    
    /**
     * Factory to create the null false predicate.
     * 
     * @param predicate  the predicate to decorate, not null
     * @return the predicate
     * @throws IllegalArgumentException if the predicate is null
     */
    public static Predicate getInstance(Predicate predicate) {
        if (predicate == null) {
            throw new IllegalArgumentException("Predicate must not be null");
        }
        return new NullIsFalsePredicate(predicate);
    }

    /**
     * Constructor that performs no validation.
     * Use <code>getInstance if you want that.
     * 
     * @param predicate  the predicate to call after the null check
     */
    public NullIsFalsePredicate(Predicate predicate) {
        super();
        iPredicate = predicate;
    }

    /**
     * Evaluates the predicate returning the result of the decorated predicate
     * once a null check is performed.
     * 
     * @param object  the input object
     * @return true if decorated predicate returns true, false if input is null
     */
    public boolean evaluate(Object object) {
        if (object == null) {
            return false;
        }
        return iPredicate.evaluate(object);
    }

    /**
     * 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};
    }

}

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