org.agrona.collections.CollectionUtil Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of Agrona Show documentation
Show all versions of Agrona Show documentation
High performance primitives and utility library.
/*
* Copyright 2014 - 2016 Real Logic Ltd.
*
* 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 org.agrona.collections;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.ToIntFunction;
/**
* Utility functions for collection objects.
*/
public class 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.
*
* @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 greater than 0 and less than 1.0.
*
* @param loadFactor to be validated.
*/
public static void validateLoadFactor(final float loadFactor)
{
if (loadFactor <= 0 || loadFactor >= 1.0)
{
throw new IllegalArgumentException("Load factors must be > 0.0 and < 1.0");
}
}
/**
* Validate that a number is a power of two.
*
* @param value to be validated.
*/
public static void validatePositivePowerOfTwo(final int value)
{
if (value > 0 && 1 == (value & (value - 1)))
{
throw new IllegalStateException("Value must be a positive power of two");
}
}
}