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 */ 017package org.apache.camel.util.function; 018 019import java.util.Objects; 020import java.util.Optional; 021import java.util.concurrent.atomic.AtomicReference; 022import java.util.function.Consumer; 023import java.util.function.Predicate; 024import java.util.function.Supplier; 025 026public final class Suppliers { 027 private Suppliers() { 028 } 029 030 public static <T> Supplier<T> memorize(Supplier<T> supplier) { 031 final AtomicReference<T> valueHolder = new AtomicReference<>(); 032 return () -> { 033 T supplied = valueHolder.get(); 034 if (supplied == null) { 035 synchronized (valueHolder) { 036 supplied = valueHolder.get(); 037 if (supplied == null) { 038 supplied = Objects.requireNonNull(supplier.get(), "Supplier should not return null"); 039 valueHolder.lazySet(supplied); 040 } 041 } 042 } 043 return supplied; 044 }; 045 } 046 047 public static <T> Supplier<T> memorize(ThrowingSupplier<T, ? extends Exception> supplier, Consumer<Exception> consumer) { 048 final AtomicReference<T> valueHolder = new AtomicReference<>(); 049 return () -> { 050 T supplied = valueHolder.get(); 051 if (supplied == null) { 052 synchronized (valueHolder) { 053 supplied = valueHolder.get(); 054 if (supplied == null) { 055 try { 056 supplied = Objects.requireNonNull(supplier.get(), "Supplier should not return null"); 057 valueHolder.lazySet(supplied); 058 } catch (Exception e) { 059 consumer.accept(e); 060 } 061 } 062 } 063 } 064 return supplied; 065 }; 066 } 067 068 public static <T> Optional<T> firstNotNull(ThrowingSupplier<T, Exception>... suppliers) throws Exception { 069 T answer = null; 070 071 for (int i = 0; i < suppliers.length; i++) { 072 answer = suppliers[i].get(); 073 if (answer != null) { 074 break; 075 } 076 } 077 078 return Optional.ofNullable(answer); 079 } 080 081 public static <T> Optional<T> firstMatching(Predicate<T> predicate, ThrowingSupplier<T, Exception>... suppliers) throws Exception { 082 T answer = null; 083 084 for (int i = 0; i < suppliers.length; i++) { 085 answer = suppliers[i].get(); 086 if (predicate.test(answer)) { 087 break; 088 } 089 } 090 091 return Optional.ofNullable(answer); 092 } 093}