com.hazelcast.util.CollectionUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2018, 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.util;
import com.hazelcast.nio.serialization.Data;
import com.hazelcast.spi.serialization.SerializationService;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import static com.hazelcast.util.Preconditions.checkNotNull;
/**
* Various collection utility methods.
*/
public final class CollectionUtil {
private CollectionUtil() {
}
/**
* Returns {@code true} if the given collection is {@code null} or empty, otherwise returns {@code false}.
*
* @param collection the given collection
* @return {@code true} if collection is empty
*/
public static boolean isEmpty(Collection collection) {
return collection == null || collection.isEmpty();
}
/**
* Returns {@code true} if the given collection is not {@code null} and not empty, otherwise returns {@code false}.
*
* @param collection the given collection
* @return {@code true} if collection is not empty
*/
public static boolean isNotEmpty(Collection collection) {
return !isEmpty(collection);
}
/**
* Adds a value to a list of values in the map.
*
* Creates a new list if no list is found for the key.
*
* @param map the given map of lists
* @param key the key of the target list
* @param value the value to add to the target list
* @return the updated list of values
*/
public static List addToValueList(Map> map, K key, V value) {
List valueList = map.get(key);
if (valueList == null) {
valueList = new ArrayList();
map.put(key, valueList);
}
valueList.add(value);
return valueList;
}
/**
* Returns the n-th item or {@code null} if collection is smaller.
*
* @param collection the given collection
* @param position position of the wanted item
* @return the item on position or {@code null} if the given collection is too small
* @throws NullPointerException if collection is {@code null}
*/
public static T getItemAtPositionOrNull(Collection collection, int position) {
if (position >= collection.size()) {
return null;
}
if (collection instanceof List) {
return ((List) collection).get(position);
}
Iterator iterator = collection.iterator();
T item = null;
for (int i = 0; i < position + 1; i++) {
item = iterator.next();
}
return item;
}
/**
* Converts a collection of any type to a collection of {@link Data}.
*
* @param collection the given collection
* @param serializationService will be used for converting object to {@link Data}
* @return collection of data
* @throws NullPointerException if collection is {@code null} or contains a {@code null} item
*/
public static Collection objectToDataCollection(Collection collection,
SerializationService serializationService) {
List dataCollection = new ArrayList(collection.size());
objectToDataCollection(collection, dataCollection, serializationService, null);
return dataCollection;
}
/**
* Converts a collection of any type to a collection of {@link Data}.
*
* @param objectCollection object items
* @param dataCollection data items
* @param serializationService will be used for converting object to {@link Data}
* @param errorMessage the errorMessage when an item is null
* @throws NullPointerException if collection is {@code null} or contains a {@code null} item
*/
public static void objectToDataCollection(Collection objectCollection, Collection dataCollection,
SerializationService serializationService, String errorMessage) {
for (C item : objectCollection) {
checkNotNull(item, errorMessage);
dataCollection.add(serializationService.toData(item));
}
}
/**
* Converts a {@link Collection} to a primitive {@code int[]} array.
*
* @param collection the given collection
* @return a primitive int[] array
* @throws NullPointerException if collection is {@code null}
*/
public static int[] toIntArray(Collection collection) {
int[] collectionArray = new int[collection.size()];
int index = 0;
for (Integer item : collection) {
collectionArray[index++] = item;
}
return collectionArray;
}
/**
* Converts a {@link Collection} to a primitive {@code long[]} array.
*
* @param collection the given collection
* @return a primitive long[] array
* @throws NullPointerException if collection is {@code null}
*/
public static long[] toLongArray(Collection collection) {
long[] collectionArray = new long[collection.size()];
int index = 0;
for (Long item : collection) {
collectionArray[index++] = item;
}
return collectionArray;
}
/**
* Converts an int array to an Integer {@link List}.
*
* The returned collection can be modified after it is created; it isn't protected by an immutable wrapper.
*
* @param array the array
* @return the list.
* throws {@link NullPointerException} if array is null.
*/
public static List toIntegerList(int[] array) {
List result = new ArrayList(array.length);
for (int partitionId : array) {
result.add(partitionId);
}
return result;
}
/** Returns an empty Collection if argument is null. **/
public static Collection nullToEmpty(Collection collection) {
return collection == null ? Collections.emptyList() : collection;
}
}