content: /*
   * Copyright 2017 The Android Open Source Project
   *
   * Licensed 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 android.app.servertransaction;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * An object pool that can provide reused objects if available.
   * @hide
   */
  class ObjectPool {
  
      private static final Object sPoolSync = new Object();
      private static final Map<Class, ArrayList<? extends ObjectPoolItem>> sPoolMap =
              new HashMap<>();
  
      private static final int MAX_POOL_SIZE = 50;
  
      /**
       * Obtain an instance of a specific class from the pool
       * @param itemClass The class of the object we're looking for.
       * @return An instance or null if there is none.
       */
      public static <T extends ObjectPoolItem> T obtain(Class<T> itemClass) {
          synchronized (sPoolSync) {
              @SuppressWarnings("unchecked")
              final ArrayList<T> itemPool = (ArrayList<T>) sPoolMap.get(itemClass);
              if (itemPool != null && !itemPool.isEmpty()) {
                  return itemPool.remove(itemPool.size() - 1);
              }
              return null;
          }
      }
  
      /**
       * Recycle the object to the pool. The object should be properly cleared before this.
       * @param item The object to recycle.
       * @see ObjectPoolItem#recycle()
       */
      public static <T extends ObjectPoolItem> void recycle(T item) {
          synchronized (sPoolSync) {
              @SuppressWarnings("unchecked")
              ArrayList<T> itemPool = (ArrayList<T>) sPoolMap.get(item.getClass());
              if (itemPool == null) {
                  itemPool = new ArrayList<>();
                  sPoolMap.put(item.getClass(), itemPool);
              }
              // Check if the item is already in the pool
              final int size = itemPool.size();
              for (int i = 0; i < size; i++) {
                  if (itemPool.get(i) == item) {
                      throw new IllegalStateException("Trying to recycle already recycled item");
                  }
              }
  
              if (size < MAX_POOL_SIZE) {
                  itemPool.add(item);
              }
          }
      }
  }
  