com.azure.cosmos.implementation.apachecommons.collections.CollectionUtils Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
/*
* Portions Copyright (c) Microsoft Corporation
*/
package com.azure.cosmos.implementation.apachecommons.collections;
import java.util.Collection;
import java.util.Collections;
public class CollectionUtils {
/**
* An empty unmodifiable collection.
* The JDK provides empty Set and List implementations which could be used for
* this purpose. However they could be cast to Set or List which might be
* undesirable. This implementation only implements Collection.
*/
@SuppressWarnings("rawtypes") // we deliberately use the raw type here
public static final Collection EMPTY_COLLECTION = Collections.emptyList();
private CollectionUtils() {}
/**
* Returns the immutable EMPTY_COLLECTION with generic type safety.
*
* @see #EMPTY_COLLECTION
* @param the element type
* @return immutable empty collection
*/
@SuppressWarnings("unchecked") // OK, empty collection is compatible with any type
public static Collection emptyCollection() {
return EMPTY_COLLECTION;
}
/**
* Returns an immutable empty collection if the argument is null
,
* or the argument itself otherwise.
*
* @param the element type
* @param collection the collection, possibly null
* @return an empty collection if the argument is null
*/
public static Collection emptyIfNull(final Collection collection) {
return collection == null ? CollectionUtils.emptyCollection() : collection;
}
}