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1   /*
2    *  Copyright 2001-2007 Stephen Colebourne
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package org.joda.time.field;
17  
18  import org.joda.time.Chronology;
19  import org.joda.time.DateTimeField;
20  
21  /**
22   * Converts a strict DateTimeField into a lenient one. By being lenient, the
23   * set method accepts out of bounds values, performing an addition instead.
24   * <p>
25   * LenientDateTimeField is thread-safe and immutable.
26   *
27   * @author Brian S O'Neill
28   * @see org.joda.time.chrono.LenientChronology
29   * @see StrictDateTimeField
30   * @since 1.0
31   */
32  public class LenientDateTimeField extends DelegatedDateTimeField {
33  
34      private static final long serialVersionUID = 8714085824173290599L;
35  
36      private final Chronology iBase;
37  
38      /**
39       * Returns a lenient version of the given field. If it is already lenient,
40       * then it is returned as-is. Otherwise, a new LenientDateTimeField is
41       * returned.
42       */
43      public static DateTimeField getInstance(DateTimeField field, Chronology base) {
44          if (field == null) {
45              return null;
46          }
47          if (field instanceof StrictDateTimeField) {
48              field = ((StrictDateTimeField)field).getWrappedField();
49          }
50          if (field.isLenient()) {
51              return field;
52          }
53          return new LenientDateTimeField(field, base);
54      }
55  
56      protected LenientDateTimeField(DateTimeField field, Chronology base) {
57          super(field);
58          iBase = base;
59      }
60  
61      public final boolean isLenient() {
62          return true;
63      }
64  
65      /**
66       * Set values which may be out of bounds by adding the difference between
67       * the new value and the current value.
68       */
69      public long set(long instant, int value) {
70          // lenient needs to handle time zone chronologies
71          // so we do the calculation using local milliseconds
72          long localInstant = iBase.getZone().convertUTCToLocal(instant);
73          long difference = FieldUtils.safeSubtract(value, get(instant));
74          localInstant = getType().getField(iBase.withUTC()).add(localInstant, difference);
75          return iBase.getZone().convertLocalToUTC(localInstant, false, instant);
76      }
77  }