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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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/*
 * 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.lang3.function;

import java.util.function.Function;

/**
 * Factory for {@link Function}.
 *
 * @since 3.14.0
 */
public final class Functions {

    /**
     * Applies the {@link Function} on the object if the function is not {@code null}. Otherwise, does nothing and returns {@code null}.
     *
     * @param function the function to apply.
     * @param object   the object to apply the function.
     *
     * @param       the type of the argument the function applies.
     * @param       the type of the result the function returns.
     * @return the value the function returns if the function is not {@code null}; {@code null} otherwise.
     * @since 3.15.0
     */
    public static  R apply(final Function function, final T object) {
        return function != null ? function.apply(object) : null;
    }

    /**
     * Starts a fluent chain like {@code function(foo::bar).andThen(...).andThen(...).apply(...);}
     *
     * @param       Input type.
     * @param       Return type.
     * @param function the argument to return.
     * @return the argument
     */
    public static  Function function(final Function function) {
        return function;
    }

    private Functions() {
        // no instances needed.
    }
}