com.hazelcast.internal.util.MapUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2020, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.internal.util;
import com.hazelcast.internal.util.collection.Int2ObjectHashMap;
import java.util.AbstractMap.SimpleImmutableEntry;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* Utility class for Maps
*/
public final class MapUtil {
/**
* Default hash map load factor.
*/
public static final float HASHMAP_DEFAULT_LOAD_FACTOR = 0.75f;
private MapUtil() { }
/**
* Utility method that creates an {@link java.util.HashMap} with its initialCapacity calculated
* to minimize rehash operations
*/
public static Map createHashMap(int expectedMapSize) {
final int initialCapacity = calculateInitialCapacity(expectedMapSize);
return new HashMap<>(initialCapacity, HASHMAP_DEFAULT_LOAD_FACTOR);
}
/**
* Utility method that creates an {@link java.util.LinkedHashMap} with its initialCapacity calculated
* to minimize rehash operations
*/
public static Map createLinkedHashMap(int expectedMapSize) {
final int initialCapacity = calculateInitialCapacity(expectedMapSize);
return new LinkedHashMap<>(initialCapacity, HASHMAP_DEFAULT_LOAD_FACTOR);
}
/**
* Utility method that creates an {@link java.util.LinkedHashMap} with its initialCapacity calculated
* to minimize rehash operations
*/
public static ConcurrentMap createConcurrentHashMap(int expectedMapSize) {
//concurrent hash map will size itself to accomodate this many elements
return new ConcurrentHashMap<>(expectedMapSize);
}
/**
* Utility method that creates an {@link Int2ObjectHashMap} with its initialCapacity calculated
* to minimize rehash operations
*/
public static Int2ObjectHashMap createInt2ObjectHashMap(int expectedMapSize) {
final int initialCapacity = (int) (expectedMapSize / Int2ObjectHashMap.DEFAULT_LOAD_FACTOR) + 1;
return new Int2ObjectHashMap<>(initialCapacity, Int2ObjectHashMap.DEFAULT_LOAD_FACTOR);
}
/**
* Returns the initial hash map capacity needed for the expected map size.
* To avoid resizing the map, the initial capacity should be different than
* the expected size, depending on the load factor.
*
* @param expectedMapSize the expected map size
* @return the necessary initial capacity
* @see HashMap
*/
public static int calculateInitialCapacity(int expectedMapSize) {
return (int) (expectedMapSize / HASHMAP_DEFAULT_LOAD_FACTOR) + 1;
}
/**
* Test the given map and return {@code true} if the map is null or empty.
* @param map the map to test
* @return {@code true} if {@code map} is null or empty, otherwise {@code false}.
*/
public static boolean isNullOrEmpty(Map map) {
return map == null || map.isEmpty();
}
/**
* Returns a {@code Map.Entry} with the given key and value.
*/
public static Map.Entry entry(K k, V v) {
return new SimpleImmutableEntry<>(k, v);
}
/**
* Converts long map size to int.
* If size is greater than Integer.MAX_VALUE
* then Integer.MAX_VALUE is returned.
*
* @param size map size
* @return map size in int type
*/
public static int toIntSize(long size) {
assert size >= 0 : "Invalid size value: " + size;
return size > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) size;
}
}