com.gemstone.gemfire.internal.util.CollectionUtils Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of gemfire-core Show documentation
Show all versions of gemfire-core Show documentation
SnappyData store based off Pivotal GemFireXD
The newest version!
/*
* Copyright (c) 2010-2015 Pivotal Software, 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. See accompanying
* LICENSE file.
*/
package com.gemstone.gemfire.internal.util;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import com.gemstone.gemfire.internal.lang.Filter;
/**
* The CollectionUtils class is a utility class for working with the Java Collections framework of classes, data
* structures and algorithms.
*
* @author John Blum
* @see com.gemstone.gemfire.internal.lang.Filter
* @see java.util.Arrays
* @see java.util.Collection
* @see java.util.Collections
* @see java.util.Iterator
* @see java.util.List
* @see java.util.Map
* @see java.util.Set
* @since 7.0
*/
@SuppressWarnings("unused")
public abstract class CollectionUtils {
/**
* Returns the specified array as a List of elements.
*
* @param the class type of the elements in the array.
* @param array the object array of elements to convert to a List.
* @return a List of elements contained in the specified array.
* @see java.util.Arrays#asList(Object[])
*/
public static List asList(final T... array) {
return new ArrayList(Arrays.asList(array));
}
/**
* Returns the specified array as a Set of elements.
*
* @param the class type of the elements in the array.
* @param array the object array of elements to convert to a Set.
* @return a Set of elements contained in the specified array.
* @see java.util.Arrays#asList(Object[])
*/
public static Set asSet(final T... array) {
return new HashSet(Arrays.asList(array));
}
/**
* Null-safe implementation for method invocations that return a List Collection. If the returned List is null,
* then this method will return an empty List in it's place.
*
* @param the class type of the List's elements.
* @param list the target List to verify as not null.
* @return the specified List if not null otherwise return an empty List.
*/
public static List emptyList(final List list) {
return (list != null ? list : Collections.emptyList());
}
/**
* Null-safe implementation for method invocations that return a Set Collection. If the returned Set is null,
* then this method will return an empty Set in it's place.
*
* @param the class type of the Set's elements.
* @param set the target Set to verify as not null.
* @return the specified Set if not null otherwise return an empty Set.
*/
public static Set emptySet(final Set set) {
return (set != null ? set : Collections.emptySet());
}
/**
* Iterates the Collection and finds all object elements that match the Filter criteria.
*
* @param the class type of the Collection elements.
* @param collection the Collection of elements to iterate and filter.
* @param filter the Filter applied to the Collection of elements in search of all matching elements.
* @return a List of elements from the Collection matching the criteria of the Filter in the order in which they were
* found. If no elements match the Filter criteria, then an empty List is returned.
*/
public static List findAll(final Collection collection, final Filter filter) {
final List matches = new ArrayList(collection.size());
for (final T element : collection) {
if (filter.accept(element)) {
matches.add(element);
}
}
return matches;
}
/**
* Iterates the Collection and finds all object elements that match the Filter criteria.
*
* @param the class type of the Collection elements.
* @param collection the Collection of elements to iterate and filter.
* @param filter the Filter applied to the Collection of elements in search of the matching element.
* @return a single element from the Collection that match the criteria of the Filter. If multiple elements match
* the Filter criteria, then this method will return the first one. If no element of the Collection matches
* the criteria of the Filter, then this method returns null.
*/
public static T findBy(final Collection collection, final Filter filter) {
for (T element : collection) {
if (filter.accept(element)) {
return element;
}
}
return null;
}
/**
* Removes keys from the Map based on a Filter.
*
* @param the Class type of the key.
* @param the Class type of the value.
* @param map the Map from which to remove key-value pairs based on a Filter.
* @param filter the Filter to apply to the Map entries to ascertain their "value".
* @return the Map with entries filtered by the specified Filter.
* @see java.util.Map
* @see java.util.Map.Entry
* @see com.gemstone.gemfire.internal.lang.Filter
*/
public static Map removeKeys(final Map map, final Filter> filter) {
for (final Iterator> mapEntries = map.entrySet().iterator(); mapEntries.hasNext(); ) {
if (!filter.accept(mapEntries.next())) {
mapEntries.remove();
}
}
return map;
}
/**
* Removes keys with null values in the Map.
*
* @param map the Map from which to remove null key-value pairs.
* @return the Map without any null keys or values.
* @see #removeKeys
* @see java.util.Map
*/
public static Map removeKeysWithNullValues(final Map map) {
return removeKeys(map, new Filter>() {
@Override public boolean accept(final Map.Entry entry) {
return (entry.getValue() != null);
}
});
}
}