/*
 * 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.collections4.functors;

import java.io.Serializable;

import org.apache.commons.collections4.Factory;

Factory implementation that returns the same constant each time.

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:
3.0/**
 * 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.
 * </p>
 *
 * @since 3.0
 */
public class ConstantFactory<T> implements Factory<T>, Serializable {

    
Serial version UID /** Serial version UID */
    private static final long serialVersionUID = -3520677225766901240L;

    
Returns null each time /** Returns null each time */
    @SuppressWarnings("rawtypes") // The null factory works for all object types
    public static final Factory NULL_INSTANCE = new ConstantFactory<>(null);

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

    
Factory method that performs validation.
Params:
constantToReturn –  the constant object to return each time in the factory
Type parameters:
<T> –  the type of the constant
Returns:
the constant factory./**
     * Factory method that performs validation.
     *
     * @param <T>  the type of the constant
     * @param constantToReturn  the constant object to return each time in the factory
     * @return the <code>constant</code> factory.
     */
    public static <T> Factory<T> constantFactory(final T constantToReturn) {
        if (constantToReturn == null) {
            return NULL_INSTANCE;
        }
        return new ConstantFactory<>(constantToReturn);
    }

    
Constructor that performs no validation.
Use constantFactory if you want that.
Params:
constantToReturn –  the constant to return each time/**
     * Constructor that performs no validation.
     * Use <code>constantFactory</code> if you want that.
     *
     * @param constantToReturn  the constant to return each time
     */
    public ConstantFactory(final T constantToReturn) {
        super();
        iConstant = constantToReturn;
    }

    
Always return constant.
Returns:
the stored constant value/**
     * Always return constant.
     *
     * @return the stored constant value
     */
    @Override
    public T create() {
        return iConstant;
    }

    
Gets the constant.
Returns:
the constant
Since:
3.1/**
     * Gets the constant.
     *
     * @return the constant
     * @since 3.1
     */
    public T getConstant() {
        return iConstant;
    }

}