    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 *      https://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.Supplier;
    021
    022/**
    023 * Helps use {@link Supplier}.
    024 *
    025 * @since 3.13.0
    026 */
    027public class Suppliers {
    028
    029    /**
    030     * Returns the singleton supplier that always returns null.
    031     * <p>
    032     * This supplier never throws an exception.
    033     * </p>
    034     */
    035    @SuppressWarnings("rawtypes")
    036    private static Supplier NUL = () -> null;
    037
    038    /**
    039     * Null-safe call to {@link Supplier#get()}.
    040     *
    041     * @param <T> the type of results supplied by this supplier.
    042     * @param supplier the supplier or null.
    043     * @return Result of {@link Supplier#get()} or null.
    044     */
    045    public static <T> T get(final Supplier<T> supplier) {
    046        return supplier == null ? null : supplier.get();
    047    }
    048
    049    /**
    050     * Gets the singleton supplier that always returns null.
    051     * <p>
    052     * This supplier never throws an exception.
    053     * </p>
    054     *
    055     * @param <T> Supplied type.
    056     * @return The NUL singleton.
    057     * @since 3.14.0
    058     */
    059    @SuppressWarnings("unchecked")
    060    public static <T> Supplier<T> nul() {
    061        return NUL;
    062    }
    063
    064    /**
    065     * Make private in 4.0.
    066     *
    067     * @deprecated TODO Make private in 4.0.
    068     */
    069    @Deprecated
    070    public Suppliers() {
    071        // empty
    072    }
    073}