1   /* Copyright 2002-2025 CS GROUP
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS 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  package org.orekit.utils.units;
18  
19  import java.util.HashMap;
20  import java.util.Map;
21  
22  /** Cache for parsed units.
23   * @author Luc Maisonobe
24   * @since 11.0
25   */
26  public class UnitsCache {
27  
28      /** Parsed units cache. */
29      private final Map<String, Unit> cache;
30  
31      /** Simple constructor.
32       */
33      public UnitsCache() {
34          this.cache = new HashMap<>();
35      }
36  
37      /** Get units from a string specification.
38       * <p>
39       * Parsing is performed only the first time a specification is
40       * encountered, so the cache speeds up cases where the same
41       * units is encountered many times (for example when parsing
42       * CCSDS messages with many entries).
43       * </p>
44       * @param specification units specification (may be null)
45       * @return parsed units ({@link Unit#NONE} if specification is null)
46       */
47      public Unit getUnits(final String specification) {
48  
49          if (specification == null || specification.isEmpty()) {
50              return Unit.NONE;
51          }
52  
53          synchronized (cache) {
54              return cache.computeIfAbsent(specification, s -> Unit.parse(specification));
55          }
56  
57      }
58  
59  }