    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}