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/*
* 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.
*/
package io.microsphere.collection;
import io.microsphere.util.BaseUtils;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import static io.microsphere.util.ArrayUtils.length;
/**
* The utilities class for Java Collection
*
* @author Mercy
* @version 1.0.0
* @see Collections
*/
public abstract class CollectionUtils extends BaseUtils {
public static boolean isEmpty(Collection collection) {
return collection == null || collection.isEmpty();
}
public static boolean isNotEmpty(Collection collection) {
return !isEmpty(collection);
}
public static Iterable toIterable(Collection collection) {
return collection;
}
public static Iterable toIterable(Iterator iterator) {
return new IterableAdapter(iterator);
}
public static Iterator toIterator(Enumeration enumeration) {
return new EnumerationIteratorAdapter(enumeration);
}
public static Iterable toIterable(Enumeration enumeration) {
return toIterable(toIterator(enumeration));
}
public static Iterable singletonIterable(E element) {
return toIterable(singletonIterator(element));
}
public static Iterator singletonIterator(E element) {
return new SingletonIterator<>(element);
}
public static Enumeration singletonEnumeration(E element) {
return new SingletonEnumeration<>(element);
}
public static Iterator unmodifiableIterator(Iterator iterator) {
return new UnmodifiableIterator(iterator);
}
/**
* Get the size of the specified {@link Collection}
*
* @param collection the specified {@link Collection}
* @return must be positive number
*/
public static int size(Collection collection) {
return collection == null ? 0 : collection.size();
}
/**
* Get the size of the specified {@link Iterable}
*
* @param iterable the specified {@link Iterable}
* @return must be positive number
*/
public static int size(Iterable iterable) {
if (iterable instanceof Collection) {
return size((Collection) iterable);
}
Iterator iterator = iterable.iterator();
int size = 0;
while (iterator.hasNext()) {
iterator.next();
size++;
}
return size;
}
/**
* Compares the specified collection with another, the main implementation references
* {@link AbstractSet}
*
* @param one {@link Collection}
* @param another {@link Collection}
* @return if equals, return true, or false
*/
public static boolean equals(Collection one, Collection another) {
if (one == another) {
return true;
}
if (isEmpty(one) && isEmpty(another)) {
return true;
}
if (size(one) != size(another)) {
return false;
}
try {
return one.containsAll(another);
} catch (ClassCastException | NullPointerException unused) {
return false;
}
}
/**
* Add the multiple values into {@link Collection the specified collection}
*
* @param collection {@link Collection the specified collection}
* @param values the multiple values
* @param the type of values
* @return the effected count after added
*/
public static int addAll(Collection collection, T... values) {
int size = length(values);
if (size < 1) {
return 0;
}
if (collection == null) {
return 0;
}
int effectedCount = 0;
for (int i = 0; i < size; i++) {
if (collection.add(values[i])) {
effectedCount++;
}
}
return effectedCount;
}
/**
* Take the first element from the specified collection
*
* @param values the collection object
* @param the type of element of collection
* @return if found, return the first one, or null
*/
public static T first(Collection values) {
if (isEmpty(values)) {
return null;
}
if (values instanceof List) {
List list = (List) values;
return list.get(0);
} else {
return first((Iterable) values);
}
}
/**
* Take the first element from the specified {@link Iterable}
*
* @param values the {@link Iterable} object
* @param the type of element of {@link Iterable}
* @return if found, return the first one, or null
*/
public static T first(Iterable values) {
return values == null ? null : first(values.iterator());
}
/**
* Take the first element from the specified {@lin Iterator}
*
* @param values the {@link Iterator} object
* @param the type of element of {@lin Iterator}
* @return if found, return the first one, or null
*/
public static T first(Iterator values) {
if (values == null || !values.hasNext()) {
return null;
}
return values.next();
}
}