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Commons Collections example source code file (ConstantFactory.java)

This example Commons Collections source code file (ConstantFactory.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

constantfactory, constantfactory, factory, factory, io, null_instance, null_instance, object, object, serializable

The Commons Collections ConstantFactory.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.Factory;

/**
 * Factory implementation that returns the same constant each time.
 * <p>
 * No check is made that the object is immutable. In general, only immutable
 * objects should use the constant factory. Mutable objects should
 * use the prototype factory.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class ConstantFactory implements Factory, Serializable {

    /** Serial version UID */
    private static final long serialVersionUID = -3520677225766901240L;
    
    /** Returns null each time */
    public static final Factory NULL_INSTANCE = new ConstantFactory(null);

    /** The closures to call in turn */
    private final Object iConstant;

    /**
     * Factory method that performs validation.
     *
     * @param constantToReturn  the constant object to return each time in the factory
     * @return the <code>constant factory.
     */
    public static Factory getInstance(Object constantToReturn) {
        if (constantToReturn == null) {
            return NULL_INSTANCE;
        }
        return new ConstantFactory(constantToReturn);
    }
    
    /**
     * Constructor that performs no validation.
     * Use <code>getInstance if you want that.
     * 
     * @param constantToReturn  the constant to return each time
     */
    public ConstantFactory(Object constantToReturn) {
        super();
        iConstant = constantToReturn;
    }

    /**
     * Always return constant.
     * 
     * @return the stored constant value
     */
    public Object create() {
        return iConstant;
    }

    /**
     * Gets the constant.
     * 
     * @return the constant
     * @since Commons Collections 3.1
     */
    public Object getConstant() {
        return iConstant;
    }

}

Other Commons Collections examples (source code examples)

Here is a short list of links related to this Commons Collections ConstantFactory.java source code file:

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