001/**
002 * Copyright (C) 2006-2024 Talend Inc. - www.talend.com
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.talend.sdk.component.runtime.manager.util;
017
018import static java.util.Optional.ofNullable;
019import static lombok.AccessLevel.PRIVATE;
020
021import java.util.Optional;
022import java.util.concurrent.atomic.AtomicReference;
023import java.util.function.Supplier;
024
025import lombok.NoArgsConstructor;
026
027@NoArgsConstructor(access = PRIVATE)
028public class Lazy {
029
030    public static <T> Supplier<T> lazy(final Supplier<T> decorated) {
031        final AtomicReference<Optional<T>> value = new AtomicReference<>();
032        return () -> {
033            Optional<T> t = value.get();
034            if (t == null || !t.isPresent()) {
035                synchronized (decorated) {
036                    t = value.get();
037                    if (t == null || !t.isPresent()) {
038                        t = ofNullable(decorated.get()); // optional to cache null case
039                        value.set(t);
040                    }
041                }
042            }
043            return t.orElse(null);
044        };
045    }
046}