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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.maven.scm.util;
20  
21  import java.lang.ref.SoftReference;
22  import java.text.DateFormat;
23  import java.text.FieldPosition;
24  import java.text.ParsePosition;
25  import java.text.SimpleDateFormat;
26  import java.util.Date;
27  
28  /**
29   * Thread-safe version of java.text.DateFormat.
30   * You can declare it as a static final variable:
31   * @author Olivier Lamy
32   * <code>
33   * private static final ThreadSafeDateFormat DATE_FORMAT = new ThreadSafeDateFormat( DATE_PATTERN );
34   * </code>
35   */
36  public class ThreadSafeDateFormat extends DateFormat {
37      private static final long serialVersionUID = 3786090697869963812L;
38  
39      private final String dateFormat;
40  
41      public ThreadSafeDateFormat(String sDateFormat) {
42          dateFormat = sDateFormat;
43      }
44  
45      private final ThreadLocal<SoftReference<SimpleDateFormat>> formatCache =
46              new ThreadLocal<SoftReference<SimpleDateFormat>>() {
47                  public SoftReference<SimpleDateFormat> get() {
48                      SoftReference<SimpleDateFormat> softRef = super.get();
49                      if (softRef == null || softRef.get() == null) {
50                          softRef = new SoftReference<SimpleDateFormat>(new SimpleDateFormat(dateFormat));
51                          super.set(softRef);
52                      }
53                      return softRef;
54                  }
55              };
56  
57      private DateFormat getDateFormat() {
58          return formatCache.get().get();
59      }
60  
61      public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
62          return getDateFormat().format(date, toAppendTo, fieldPosition);
63      }
64  
65      public Date parse(String source, ParsePosition pos) {
66          return getDateFormat().parse(source, pos);
67      }
68  }