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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  
18  package org.apache.logging.log4j.util;
19  
20  import org.apache.logging.log4j.message.Message;
21  import org.apache.logging.log4j.message.MessageFactory;
22  
23  
24  /**
25   * Utility class for lambda support.
26   */
27  public final class LambdaUtil {
28      /**
29       * Private constructor: this class is not intended to be instantiated.
30       */
31      private LambdaUtil() {
32      }
33  
34      /**
35       * Converts an array of lambda expressions into an array of their evaluation results.
36       *
37       * @param suppliers an array of lambda expressions or {@code null}
38       * @return an array containing the results of evaluating the lambda expressions (or {@code null} if the suppliers
39       *         array was {@code null}
40       */
41      public static Object[] getAll(final Supplier<?>... suppliers) {
42          if (suppliers == null) {
43              return null;
44          }
45          final Object[] result = new Object[suppliers.length];
46          for (int i = 0; i < result.length; i++) {
47              result[i] = get(suppliers[i]);
48          }
49          return result;
50      }
51  
52      /**
53       * Returns the result of evaluating the specified function. If the supplied value is of type Message, this method
54       * returns the result of calling {@code #getFormattedMessage} on that Message.
55       * @param supplier a lambda expression or {@code null}
56       * @return the results of evaluating the lambda expression (or {@code null} if the supplier
57       *         was {@code null}
58       */
59      public static Object get(final Supplier<?> supplier) {
60          if (supplier == null) {
61              return null;
62          }
63          final Object result = supplier.get();
64          return result instanceof Message ? ((Message) result).getFormattedMessage() : result;
65      }
66  
67      /**
68       * Returns the Message supplied by the specified function.
69       * @param supplier a lambda expression or {@code null}
70       * @return the Message resulting from evaluating the lambda expression (or {@code null} if the supplier was
71       * {@code null}
72       */
73      public static Message get(final MessageSupplier supplier) {
74          if (supplier == null) {
75              return null;
76          }
77          return supplier.get();
78      }
79  
80      /**
81       * Returns a Message, either the value supplied by the specified function, or a new Message created by the specified
82       * Factory.
83       * @param supplier a lambda expression or {@code null}
84       * @return the Message resulting from evaluating the lambda expression or the Message created by the factory for
85       * supplied values that are not of type Message
86       */
87      public static Message getMessage(final Supplier<?> supplier, final MessageFactory messageFactory) {
88          if (supplier == null) {
89              return null;
90          }
91          final Object result = supplier.get();
92          return result instanceof Message ? (Message) result : messageFactory.newMessage(result);
93      }
94  }