001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.functors;
018
019import java.io.Serializable;
020
021import org.apache.commons.collections4.Closure;
022
023/**
024 * Closure implementation that does nothing.
025 *
026 * @since 3.0
027 * @version $Id: NOPClosure.html 972421 2015-11-14 20:00:04Z tn $
028 */
029public final class NOPClosure<E> implements Closure<E>, Serializable {
030
031    /** Serial version UID */
032    private static final long serialVersionUID = 3518477308466486130L;
033
034    /** Singleton predicate instance */
035    @SuppressWarnings("rawtypes")
036    public static final Closure INSTANCE = new NOPClosure<Object>();
037
038    /**
039     * Factory returning the singleton instance.
040     *
041     * @param <E> the type that the closure acts on
042     * @return the singleton instance
043     * @since 3.1
044     */
045    @SuppressWarnings("unchecked")
046    public static <E> Closure<E> nopClosure() {
047        return (Closure<E>) INSTANCE;
048    }
049
050    /**
051     * Constructor.
052     */
053    private NOPClosure() {
054        super();
055    }
056
057    /**
058     * Do nothing.
059     *
060     * @param input  the input object
061     */
062    public void execute(final E input) {
063        // do nothing
064    }
065
066    private Object readResolve() {
067        return INSTANCE;
068    }
069
070}