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.causeway.commons.collections;
  
  import java.util.ArrayList;
  import java.util.stream.Collector;
  import java.util.stream.Collectors;
  
  import lombok.experimental.UtilityClass;
  
  /**
   * As the {@link Can} interface can only provide public methods,
   * we encapsulate optimized unsafe Can constructors here with
   * package private access only.
   */
  @UtilityClass
  class _CanFactory {
  
      /**
       * @param <T> element type
       * @param nonNullElements - not containing <code>null</code>
       * @implNote no non-null checks for optimization (package internal use only)
       */
      <T> Can<T> ofNonNullElements(final ArrayList<T> nonNullElements) {
  
          if(nonNullElements.isEmpty()) {
              return Can.empty();
          }
  
          if(nonNullElements.size()==1) {
              return Can.ofSingleton(nonNullElements.get(0));
          }
  
          // let's be heap friendly, ignore below a certain threshold
          if(nonNullElements.size()>32) {
              nonNullElements.trimToSize();
          }
  
          return new Can_Multiple<>(nonNullElements);
      }
  
      <T> ArrayList<T> arrayListWithSizeUpperBound(final int maxSize) {
          // this is just an optimization, to pre-allocate a reasonable list size,
          // specifically targeted at small list sizes
          return new ArrayList<T>(Math.min(maxSize, 1024));
      }
  
      <T> Collector<T, ?, ArrayList<T>> toListWithSizeUpperBound(final int maxSize) {
          return Collectors.toCollection(()->
                  _CanFactory.arrayListWithSizeUpperBound(maxSize));
      }
  
  }
  