code: /*
   * 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.
   */
  /*
   * $Id$
   */
  
  package org.apache.xml.dtm.ref;
  
  
  /** <p>Like DTMStringPool, but threadsafe. It's been proposed that DTMs
   * share their string pool(s); that raises threadsafety issues which
   * this addresses. Of course performance is inferior to that of the
   * bare-bones version.</p>
   *
   * <p>Status: Passed basic test in main().</p>
   * */
  public class DTMSafeStringPool
  extends DTMStringPool
  {
    public synchronized void removeAllElements()
      {
        super.removeAllElements();
      }
  
    /** @return string whose value is uniquely identified by this integer index.
     * @throws java.lang.ArrayIndexOutOfBoundsException
     *  if index doesn't map to a string.
     * */ 
    public synchronized String indexToString(int i)
      throws java.lang.ArrayIndexOutOfBoundsException
      {
        return super.indexToString(i);
      }
  
    /** @return integer index uniquely identifying the value of this string. */ 
    public synchronized int stringToIndex(String s)
      {
        return super.stringToIndex(s);
      }
  
    /** Command-line unit test driver. This test relies on the fact that
     * this version of the pool assigns indices consecutively, starting
     * from zero, as new unique strings are encountered.
     */
    public static void main(String[] args)
    {
      String[] word={
        "Zero","One","Two","Three","Four","Five",
        "Six","Seven","Eight","Nine","Ten",
        "Eleven","Twelve","Thirteen","Fourteen","Fifteen",
        "Sixteen","Seventeen","Eighteen","Nineteen","Twenty",
        "Twenty-One","Twenty-Two","Twenty-Three","Twenty-Four",
        "Twenty-Five","Twenty-Six","Twenty-Seven","Twenty-Eight",
        "Twenty-Nine","Thirty","Thirty-One","Thirty-Two",
        "Thirty-Three","Thirty-Four","Thirty-Five","Thirty-Six",
        "Thirty-Seven","Thirty-Eight","Thirty-Nine"};
  
      DTMStringPool pool=new DTMSafeStringPool();
  
      System.out.println("If no complaints are printed below, we passed initial test.");
  
      for(int pass=0;pass<=1;++pass)
        {
          int i;
  
          for(i=0;i<word.length;++i)
            {
              int j=pool.stringToIndex(word[i]);
              if(j!=i)
                System.out.println("\tMismatch populating pool: assigned "+
                                   j+" for create "+i);
            }
  
          for(i=0;i<word.length;++i)
            {
              int j=pool.stringToIndex(word[i]);
              if(j!=i)
                System.out.println("\tMismatch in stringToIndex: returned "+
                                   j+" for lookup "+i);
            }
  
          for(i=0;i<word.length;++i)
            {
              String w=pool.indexToString(i);
              if(!word[i].equals(w))
                System.out.println("\tMismatch in indexToString: returned"+
                                   w+" for lookup "+i);
            }
          
          pool.removeAllElements();
          
          System.out.println("\nPass "+pass+" complete\n");
        } // end pass loop
    }
  } // DTMSafeStringPool
  