package org.apache.maven.scm.util;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import java.lang.ref.SoftReference;
  import java.text.DateFormat;
  import java.text.FieldPosition;
  import java.text.ParsePosition;
  import java.text.SimpleDateFormat;
  import java.util.Date;
  
  /**
   * Thread-safe version of java.text.DateFormat.
   * You can declare it as a static final variable:
   * @author Olivier Lamy
   * <code>
   * private static final ThreadSafeDateFormat DATE_FORMAT = new ThreadSafeDateFormat( DATE_PATTERN );
   * </code>
   */
  public class ThreadSafeDateFormat
      extends DateFormat
  {
      private static final long serialVersionUID = 3786090697869963812L;
  
      private final String m_sDateFormat;
  
      public ThreadSafeDateFormat( String sDateFormat )
      {
          m_sDateFormat = sDateFormat;
      }
  
      private final ThreadLocal<SoftReference<SimpleDateFormat>> m_formatCache = new ThreadLocal<SoftReference<SimpleDateFormat>>()
      {
          public SoftReference<SimpleDateFormat> get()
          {
              SoftReference<SimpleDateFormat> softRef = super.get();
              if ( softRef == null || softRef.get() == null )
              {
                  softRef = new SoftReference<SimpleDateFormat>( new SimpleDateFormat( m_sDateFormat ) );
                  super.set( softRef );
              }
              return softRef;
          }
      };
  
      private DateFormat getDateFormat()
      {
          return m_formatCache.get().get();
      }
  
      public StringBuffer format( Date date, StringBuffer toAppendTo, FieldPosition fieldPosition )
      {
          return getDateFormat().format( date, toAppendTo, fieldPosition );
      }
  
      public Date parse( String source, ParsePosition pos )
      {
          return getDateFormat().parse( source, pos );
      }
  }