content: /*
   * Copyright 2014-2025 Real Logic Limited.
   *
   * 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
   *
   * https://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.agrona.collections;
  
  import org.agrona.BitUtil;
  
  import java.util.List;
  import java.util.Map;
  import java.util.function.Function;
  import java.util.function.Predicate;
  import java.util.function.ToIntFunction;
  
  /**
   * Utility functions for collection objects.
   */
  public final class CollectionUtil
  {
      private CollectionUtil()
      {
      }
  
      /**
       * A getOrDefault that doesn't create garbage if its suppler is non-capturing.
       *
       * @param map      to perform the lookup on.
       * @param key      on which the lookup is done.
       * @param supplier of the default value if one is not found.
       * @param <K>      type of the key
       * @param <V>      type of the value
       * @return the value if found or a new default which as been added to the map.
       */
      public static <K, V> V getOrDefault(final Map<K, V> map, final K key, final Function<K, V> supplier)
      {
          V value = map.get(key);
          if (value == null)
          {
              value = supplier.apply(key);
              map.put(key, value);
          }
  
          return value;
      }
  
      /**
       * Garbage free sum function.
       * <p>
       * <b>Note:</b> the list must implement {@link java.util.RandomAccess} to be efficient.
       *
       * @param values   the list of input values
       * @param function function that map each value to an int
       * @param <V>      the value to add up
       * @return the sum of all the int values returned for each member of the list.
       */
      public static <V> int sum(final List<V> values, final ToIntFunction<V> function)
      {
          int total = 0;
  
          final int size = values.size();
          for (int i = 0; i < size; i++)
          {
              final V value = values.get(i);
              total += function.applyAsInt(value);
          }
  
          return total;
      }
  
      /**
       * Validate that a load factor is in the range of 0.1 to 0.9.
       * <p>
       * Load factors in the range 0.5 - 0.7 are recommended for open-addressing with linear probing.
       *
       * @param loadFactor to be validated.
       */
      public static void validateLoadFactor(final float loadFactor)
      {
          if (loadFactor < 0.1f || loadFactor > 0.9f)
          {
              throw new IllegalArgumentException("load factor must be in the range of 0.1 to 0.9: " + loadFactor);
          }
      }
  
      /**
       * Validate that a number is a power of two.
       *
       * @param value to be validated.
       */
      public static void validatePositivePowerOfTwo(final int value)
      {
          if (!BitUtil.isPowerOfTwo(value))
          {
              throw new IllegalArgumentException("value must be a positive power of two: " + value);
          }
      }
  
      /**
       * Remove element from a list if it matches a predicate.
       * <p>
       * <b>Note:</b> the list must implement {@link java.util.RandomAccess} to be efficient.
       *
       * @param values    to be iterated over.
       * @param predicate to test the value against
       * @param <T>       type of the value.
       * @return the number of items remove.
       */
      public static <T> int removeIf(final List<T> values, final Predicate<T> predicate)
      {
          int size = values.size();
          int total = 0;
  
          for (int i = 0; i < size; )
          {
              final T value = values.get(i);
              if (predicate.test(value))
              {
                  values.remove(i);
                  total++;
                  size--;
              }
              else
              {
                  i++;
              }
          }
  
          return total;
      }
  }
  