001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements. See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership. The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the  "License");
007     * you may not use this file except in compliance with the License.
008     * You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    /*
019     * $Id: StringBufferPool.java 468655 2006-10-28 07:12:06Z minchau $
020     */
021    package org.apache.xml.utils;
022    
023    /**
024     * This class pools string buffers, since they are reused so often.
025     * String buffers are good candidates for pooling, because of 
026     * their supporting character arrays.
027     * @xsl.usage internal
028     */
029    public class StringBufferPool
030    {
031    
032      /** The global pool of string buffers.   */
033      private static ObjectPool m_stringBufPool =
034        new ObjectPool(org.apache.xml.utils.FastStringBuffer.class);
035    
036      /**
037       * Get the first free instance of a string buffer, or create one 
038       * if there are no free instances.
039       *
040       * @return A string buffer ready for use.
041       */
042      public synchronized static FastStringBuffer get()
043      {
044        return (FastStringBuffer) m_stringBufPool.getInstance();
045      }
046    
047      /**
048       * Return a string buffer back to the pool.
049       *
050       * @param sb Must be a non-null reference to a string buffer.
051       */
052      public synchronized static void free(FastStringBuffer sb)
053      {
054        // Since this isn't synchronized, setLength must be 
055        // done before the instance is freed.
056        // Fix attributed to Peter Speck <speck@ruc.dk>.
057        sb.setLength(0);
058        m_stringBufPool.freeInstance(sb);
059      }
060    }