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 */
017
018package org.apache.commons.lang3.function;
019
020import java.util.function.Function;
021
022/**
023 * Factory for {@link Function}.
024 *
025 * @since 3.14.0
026 */
027public final class Functions {
028
029    /**
030     * Applies the {@link Function} on the object if the function is not {@code null}. Otherwise, does nothing and returns {@code null}.
031     *
032     * @param function the function to apply.
033     * @param object   the object to apply the function.
034     *
035     * @param <T>      the type of the argument the function applies.
036     * @param <R>      the type of the result the function returns.
037     * @return the value the function returns if the function is not {@code null}; {@code null} otherwise.
038     * @since 3.15.0
039     */
040    public static <T, R> R apply(final Function<T, R> function, final T object) {
041        return function != null ? function.apply(object) : null;
042    }
043
044    /**
045     * Starts a fluent chain like {@code function(foo::bar).andThen(...).andThen(...).apply(...);}
046     *
047     * @param <T>      Input type.
048     * @param <R>      Return type.
049     * @param function the argument to return.
050     * @return the argument
051     */
052    public static <T, R> Function<T, R> function(final Function<T, R> function) {
053        return function;
054    }
055
056    private Functions() {
057        // no instances needed.
058    }
059}