com.hazelcast.util.CollectionUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, 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 java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* Various collection utility methods, mainly targeted to use internally.
*/
public final class CollectionUtil {
private CollectionUtil() {
}
/**
* Returns {@code true} if the given collection is 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 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);
}
/**
* Add value to list of values in the map. Creates a new list if it doesn't exist for the key
*
* @param map
* @param key
* @param value
* @return the updated list of values.
*/
public static List addToValueList(Map> map, K key, V value) {
List values = map.get(key);
if (values == null) {
values = new ArrayList();
map.put(key, values);
}
values.add(value);
return values;
}
/**
* Return n-th item or null if collection is smaller
*
* @param collection
* @param position
* @param
* @return
*/
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;
}
}