content: /*
   * 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.
   */
  package org.apache.asterix.external.parser.jackson;
  
  import java.util.ArrayDeque;
  import java.util.Queue;
  
  import org.apache.asterix.om.util.container.IObjectFactory;
  
  /**
   * Object pool for DFS traversal mode, which allows to recycle objects
   * as soon as it is not needed.
   */
  public abstract class AbstractObjectPool<E, T, Q> implements IObjectPool<E> {
      private final IObjectFactory<E, T> objectFactory;
      private final Queue<Q> recycledObjects;
      private final T param;
  
      protected AbstractObjectPool(IObjectFactory<E, T> objectFactory, T param) {
          this.objectFactory = objectFactory;
          recycledObjects = new ArrayDeque<>();
          this.param = param;
      }
  
      public E getInstance() {
          E instance = unwrap(recycledObjects.poll());
          if (objectFactory != null && instance == null) {
              instance = objectFactory.create(param);
          }
          return instance;
      }
  
      public void recycle(E object) {
          if (object != null) {
              recycledObjects.add(wrap(object));
          }
      }
  
      protected abstract E unwrap(Q element);
  
      protected abstract Q wrap(E element);
  
      @Override
      public String toString() {
          return recycledObjects.toString();
      }
  }
  