001/**
002 * Copyright (C) 2006-2025 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 java.util.concurrent.locks.Lock;
019import java.util.concurrent.locks.ReentrantLock;
020import java.util.function.Supplier;
021
022/**
023 * Supplier that retains value.
024 */
025public class MemoizingSupplier<T> implements Supplier<T> {
026
027    private final Lock lock = new ReentrantLock();
028
029    private final Supplier<T> delegate;
030
031    private volatile T value = null;
032
033    public MemoizingSupplier(final Supplier<T> delegate) {
034        this.delegate = delegate;
035    }
036
037    @Override
038    public T get() {
039        if (value == null) {
040            lock.lock();
041            try {
042                if (value == null) {
043                    value = delegate.get();
044                }
045            } finally {
046                lock.unlock();
047            }
048        }
049        return value;
050    }
051}