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.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     * Returns 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}