com.fluxtion.agrona.collections.CollectionUtil Maven / Gradle / Ivy
/*
* Copyright 2014-2024 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 com.fluxtion.agrona.collections;
import com.fluxtion.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 type of the key
* @param type of the value
* @return the value if found or a new default which as been added to the map.
*/
public static V getOrDefault(final Map map, final K key, final Function supplier)
{
V value = map.get(key);
if (value == null)
{
value = supplier.apply(key);
map.put(key, value);
}
return value;
}
/**
* Garbage free sum function.
*
* Note: 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 the value to add up
* @return the sum of all the int values returned for each member of the list.
*/
public static int sum(final List values, final ToIntFunction 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.
*
* 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.
*
* Note: 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 type of the value.
* @return the number of items remove.
*/
public static int removeIf(final List values, final Predicate 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;
}
}