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/*******************************************************************************
* Copyright (c) 2018, TechEmpower, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name TechEmpower, Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL TECHEMPOWER, INC. BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*******************************************************************************/
package com.techempower.helper;
import java.util.*;
/**
* CollectionHelper provides utility functions for working with the Java
* Collections API. Most of the methods here were formerly in BasicHelper.
*/
public final class CollectionHelper
{
//
// Static methods.
//
/**
* Convenience method to return the first object in an ordered collection,
* or null if the collection is empty.
*/
public static E getFirst(Iterable objects)
{
if (objects == null)
{
return null;
}
Iterator iterator = objects.iterator();
if (!iterator.hasNext())
{
return null;
}
return iterator.next();
}
/**
* Convenience method to return the last object in an ordered collection,
* or null if the collection is empty.
*/
public static E getLast(Iterable objects)
{
if (objects == null)
{
return null;
}
if (objects instanceof List)
{
List list = (List)objects;
if (list.isEmpty())
{
return null;
}
return list.get(list.size() - 1);
}
E last = null;
for (E element : objects)
{
last = element;
}
return last;
}
/**
* Returns a random element from the list. Returns {@code null} if the list
* is null or empty.
*/
public static E getRandom(List list)
{
if (isEmpty(list))
{
return null;
}
return list.get((int)(Math.random() * list.size()));
}
/**
* Convenience method to return the first limit elements in a
* List. If objects is null, empty, or smaller than
* limit it will return objects unchanged.
*/
public static List limit(List objects, int limit)
{
if (isEmpty(objects) || objects.size() < limit)
{
return objects;
}
return objects.subList(0, limit);
}
/**
* Determines if a Collection parameter is either 1) null, or 2) empty.
*/
public static boolean isNonEmpty(Collection inputCollection)
{
return inputCollection != null && inputCollection.size() > 0;
}
/**
* Determines if a Collection parameter is either 1) null, or 2) empty.
*/
public static boolean isEmpty(Collection inputCollection)
{
return inputCollection == null || inputCollection.size() == 0;
}
/**
* Determines if a Map parameter is 1) not null, and 2) not empty.
*
* @param inputMap the Map to check
*/
public static boolean isNonEmpty(Map inputMap)
{
return inputMap != null && inputMap.size() > 0;
}
/**
* Determines if a Map parameter is either 1) null, or 2) empty.
*/
public static boolean isEmpty(Map inputMap)
{
return inputMap == null || inputMap.size() == 0;
}
/**
* Determines if an Object array parameter is 1) not null, and 2) not empty.
*
* @param inputArray the Object array to check
*/
public static boolean isNonEmpty(E[] inputArray)
{
return inputArray != null && inputArray.length > 0;
}
/**
* Determines if an Object array parameter is either 1) null, or 2) empty.
*/
public static boolean isEmpty(E[] inputArray)
{
return inputArray == null || inputArray.length == 0;
}
/**
* Returns true if the provided value is contained within the provided
* array.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static boolean arrayContains(E[] array, E valueToFind)
{
return (arrayIndexOf(array, valueToFind) >= 0);
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is not sorted. If the array is sorted, see
* Arrays.binarySearch instead.
*
* This method uses an == operator rather than an .equals call to determine
* if the provided reference is contained, not just an equivalent object.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOf(E[] array, E valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if (array[i] == valueToFind)
{
return i;
}
}
}
return -1;
}
/**
* Returns true if the provided value is contained within the provided
* array.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static boolean arrayContains(int[] array, int valueToFind)
{
return (arrayIndexOf(array, valueToFind) >= 0);
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is not sorted. If the array is sorted, see
* Arrays.binarySearch instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOf(int[] array, int valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if (array[i] == valueToFind)
{
return i;
}
}
}
return -1;
}
/**
* Returns true if the provided value is contained within the provided
* array.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static boolean arrayContains(long[] array, long valueToFind)
{
return (arrayIndexOf(array, valueToFind) >= 0);
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is not sorted. If the array is sorted, see
* Arrays.binarySearch instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOf(long[] array, long valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if (array[i] == valueToFind)
{
return i;
}
}
}
return -1;
}
/**
* Returns true if the provided value is contained within the provided
* array. Note that this method works on unsorted arrays. If the array
* is sorted, you should use Arrays.binarySearch instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static boolean arrayContains(char[] array, char valueToFind)
{
return (arrayIndexOf(array, valueToFind) >= 0);
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is not sorted. If the array is sorted, see
* Arrays.binarySearch instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOf(char[] array, char valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if (array[i] == valueToFind)
{
return i;
}
}
}
return -1;
}
/**
* Returns true if the provided value is contained within the provided
* array. Note that this method works on unsorted arrays. If the array
* is sorted, you should use Arrays.binarySearch instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static boolean arrayContains(String[] array, String valueToFind)
{
return (arrayIndexOf(array, valueToFind) >= 0);
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is -not- sorted. If the array is sorted, see Arrays.binarySearch
* instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOf(String[] array, String valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if ( ( (array[i] == null)
&& (valueToFind == null)
)
|| ( array[i].equals(valueToFind) )
)
{
return i;
}
}
}
// Default return value.
return -1;
}
/**
* Returns the index of a provided parameter within the provided array.
* Returns -1 if the item is not found. This method assumes that the
* array is -not- sorted. If the array is sorted, see Arrays.binarySearch
* instead.
*
* @param array The array to search in.
* @param valueToFind The value to search for.
*/
public static int arrayIndexOfIgnoreCase(String[] array, String valueToFind)
{
if (array != null)
{
for (int i = 0; i < array.length; i++)
{
if ( ( (array[i] == null)
&& (valueToFind == null)
)
|| ( array[i].equalsIgnoreCase(valueToFind) )
)
{
return i;
}
}
}
// Default return value.
return -1;
}
/**
* Converts the given array to a collection then to a delimiter-separated
* String.
*/
public static String toString(Object[] items, String delim)
{
return toString(toList(items), delim);
}
/**
* Converts the given collection to a delimiter-separated String by calling
* toString on each item in the collection.
*/
public static String toString(Collection collection, String delim)
{
return toString(collection, delim, "");
}
/**
* Converts the given collection to a delimiter-separated String by calling
* toString on each item in the collection.
*
* @param collection The collection to use as input.
* @param delim the delimiter.
* @param prefix an optional prefix string to append to each value.
*/
public static String toString(Collection collection, String delim,
String prefix)
{
if (isNonEmpty(collection))
{
final StringBuilder buffer = new StringBuilder();
for (Object entry : collection)
{
if (buffer.length() > 0)
{
buffer.append(delim);
}
if (StringHelper.isNonEmpty(prefix))
{
buffer.append(prefix);
}
buffer.append(entry.toString());
}
return buffer.toString();
}
return "";
}
/**
* Convert an interleaved array of objects into a Map. Every even index
* (starting at 0) will be a key followed by a value in the next index.
* E.g., ['a', 'b', 'c', 'd'] yields {'a' => 'b', 'c' => 'd'}.
*
* This version assumes a traditional map without linking (order-
* preservation) is desired.
*
* @param sourceArray an interleaved array of objects pairs to act as keys
* and values.
*/
@SafeVarargs
public static Map toMapFromInterleaved(O... sourceArray)
{
return toMapFromInterleavedImplementation(false, sourceArray);
}
/**
* Convert an interleaved array of objects into a Map. Every even index
* (starting at 0) will be a key followed by a value in the next index.
* E.g., ['a', 'b', 'c', 'd'] yields {'a' => 'b', 'c' => 'd'}.
*
* This version assumes a linked (order-preserving) map is desired so that
* the resulting map is the same as the order of sourceArray.
*
* @param sourceArray an interleaved array of objects pairs to act as keys
* and values.
*/
@SafeVarargs
public static Map toOrderedMapFromInterleaved(O... sourceArray)
{
return toMapFromInterleavedImplementation(true, sourceArray);
}
/**
* Convert an interleaved array of objects into a Map. Every even index
* (starting at 0) will be a key followed by a value in the next index.
* E.g., ['a', 'b', 'c', 'd'] yields {'a' => 'b', 'c' => 'd'}.
*
* @param preserveOrder Should a linked map be used so that iteration order
* of the resulting map is the same as the order of sourceArray?
* @param sourceArray an interleaved array of objects pairs to act as keys
* and values.
*/
@SafeVarargs
private static Map toMapFromInterleavedImplementation(boolean preserveOrder,
O... sourceArray)
{
if (sourceArray == null)
{
return null;
}
if (sourceArray.length % 2 == 1)
{
throw new IllegalArgumentException("sourceArray must contain an even number of values.");
}
// Create a LinkedHashMap if we want to preserve order. Otherwise, a
// plain HashMap will suffice.
Map toReturn = preserveOrder
? new LinkedHashMap<>(sourceArray.length / 2)
: new HashMap<>(sourceArray.length / 2);
for (int i = 0; i < sourceArray.length; i += 2)
{
toReturn.put(sourceArray[i], sourceArray[i + 1]);
}
return toReturn;
}
/**
* Convert the given Object array to a Vector.
*/
public static Vector toVector(E[] objArray)
{
Vector toReturn = new Vector<>(objArray != null ? objArray.length : 0);
for (int i = 0; objArray != null && i < objArray.length; i ++)
{
toReturn.add(objArray[i]);
}
return toReturn;
}
/**
* Creates a list from an array of objects.
*/
@SafeVarargs
public static List toList(E... objects)
{
final List list = new ArrayList<>(objects.length);
Collections.addAll(list, objects);
return list;
}
/**
* Creates a list from an iterable of objects.
*/
public static List toList(Iterable objects)
{
if (objects instanceof Collection)
{
return new ArrayList<>((Collection)objects);
}
return toList(objects.iterator());
}
/**
* Creates a list from an iterator of objects.
*/
public static List toList(Iterator objects)
{
List list = new ArrayList<>();
while (objects.hasNext())
{
list.add(objects.next());
}
return list;
}
/**
* Creates a set from an array of objects.
*/
@SafeVarargs
public static Set toSet(E... objects)
{
Set set = new HashSet<>(objects.length);
Collections.addAll(set, objects);
return set;
}
/**
* Creates a set from an iterable of objects.
*/
public static Set toSet(Iterable objects)
{
if (objects instanceof Collection)
{
return new HashSet<>((Collection)objects);
}
return toSet(objects.iterator());
}
/**
* Creates a set from an iterator of objects.
*/
public static Set toSet(Iterator objects)
{
Set set = new HashSet<>();
while (objects.hasNext())
{
set.add(objects.next());
}
return set;
}
/**
* Turns an int[] into a List of Integers.
*/
public static List toList(int[] array)
{
if (array == null)
{
return new ArrayList<>(0);
}
List list = new ArrayList<>(array.length);
for (int entry : array)
{
list.add(entry);
}
return list;
}
/**
* Turns an long[] into a List of Longs.
*/
public static List toList(long[] array)
{
if (array == null)
{
return new ArrayList<>(0);
}
List list = new ArrayList<>(array.length);
for (long entry : array)
{
list.add(entry);
}
return list;
}
/**
* Converts a String[] into an int[]. Values that cannot be parsed will be
* inserted into the array as zeros. E.g., ["1", "x"] will become int
* array [1, 0].
*/
public static int[] toIntArray(String[] strArray)
{
int[] toReturn = new int[strArray.length];
for (int i = 0; i < toReturn.length; i++)
{
toReturn[i] = NumberHelper.parseInt(strArray[i]);
}
return toReturn;
}
/**
* Converts a String[] into an long[]. Values that cannot be parsed will be
* inserted into the array as zeros. E.g., ["1", "x"] will become int
* array [1, 0].
*/
public static long[] toLongArray(String[] strArray)
{
long[] toReturn = new long[strArray.length];
for (int i = 0; i < toReturn.length; i++)
{
toReturn[i] = NumberHelper.parseLong(strArray[i]);
}
return toReturn;
}
/**
* Converts a delimited list of numbers in a String into an int array.
* For example "1,2,3,4,5" = int array [1, 2, 3, 4, 5]. Tokens that cannot
* be parsed will be inserted into the array as zeros. E.g., "1,2,x,4,5"
* will become int array [1, 2, 0, 4, 5].
*
* Returns an empty int[] if either delimitedString or delimiter are null.
*
* @param delimitedString A string composed of numbers separated by the
* delimiter.
* @param delimiter The character or characters separating each number.
*/
public static int[] toIntArray(String delimitedString, String delimiter)
{
if ( (delimitedString == null)
|| (delimiter == null)
)
{
return new int[0];
}
StringTokenizer tokenizer = new StringTokenizer(delimitedString, delimiter);
int[] toReturn = new int[tokenizer.countTokens()];
int position = 0;
while (tokenizer.hasMoreTokens())
{
toReturn[position++] = NumberHelper.parseInt(tokenizer.nextToken());
}
return toReturn;
}
/**
* Converts a delimited list of numbers in a String into a long array.
* For example "1,2,3,4,5" = long array [1, 2, 3, 4, 5]. Tokens that cannot
* be parsed will be inserted into the array as zeros. E.g., "1,2,x,4,5"
* will become int array [1, 2, 0, 4, 5].
*
* Returns an empty long[] if either delimitedString or delimiter are null.
*
* @param delimitedString A string composed of numbers separated by the
* delimiter.
* @param delimiter The character or characters separating each number.
*/
public static long[] toLongArray(String delimitedString, String delimiter)
{
if ( (delimitedString == null)
|| (delimiter == null)
)
{
return new long[0];
}
StringTokenizer tokenizer = new StringTokenizer(delimitedString, delimiter);
long[] toReturn = new long[tokenizer.countTokens()];
int position = 0;
while (tokenizer.hasMoreTokens())
{
toReturn[position++] = NumberHelper.parseLong(tokenizer.nextToken());
}
return toReturn;
}
/**
* Converts a Collection of Integer objects to a simple int[]. If the
* objects are not, in fact, Integers, an exception will be thrown.
*/
public static int[] toIntArray(Collection collectionOfIntegers)
{
int[] toReturn = new int[collectionOfIntegers.size()];
int position = 0;
for (Integer i : collectionOfIntegers)
{
toReturn[position++] = i;
}
return toReturn;
}
/**
* Converts a Collection of Long objects to a simple long[]. If the
* objects are not, in fact, Longs, an exception will be thrown.
*/
public static long[] toLongArray(Collection collectionOfLongs)
{
long[] toReturn = new long[collectionOfLongs.size()];
int position = 0;
for (Long i : collectionOfLongs)
{
toReturn[position++] = i;
}
return toReturn;
}
/**
* Converts a Collection of String objects to a simple int[] by parsing each
* String using NumberHelper.parseInt.
*/
public static int[] toIntArrayFromStrings(Collection collectionOfStrings)
{
int[] toReturn = new int[collectionOfStrings.size()];
int position = 0;
for (String s : collectionOfStrings)
{
toReturn[position++] = NumberHelper.parseInt(s);
}
return toReturn;
}
/**
* Converts a Collection of String objects to a simple long[] by parsing each
* String using NumberHelper.parseLong.
*/
public static long[] toLongArrayFromStrings(Collection collectionOfStrings)
{
long[] toReturn = new long[collectionOfStrings.size()];
int position = 0;
for (String s : collectionOfStrings)
{
toReturn[position++] = NumberHelper.parseLong(s);
}
return toReturn;
}
/**
* Converts a Collection of Strings to a String array.
*/
public static String[] toStringArray(Collection collectionOfStrings)
{
return collectionOfStrings.toArray(new String[collectionOfStrings.size()]);
}
/**
* Converts a long[] to a String[]. Does not catch any exceptions.
*/
public static String[] toStringArray(long[] intArray)
{
String[] toReturn = new String[intArray.length];
for (int i = 0; i < toReturn.length; i++)
{
toReturn[i] = "" + intArray[i];
}
return toReturn;
}
/**
* Converts an int[] to a String[]. Does not catch any exceptions.
*/
public static String[] toStringArray(int[] intArray)
{
String[] toReturn = new String[intArray.length];
for (int i = 0; i < toReturn.length; i++)
{
toReturn[i] = "" + intArray[i];
}
return toReturn;
}
/**
* Converts an byte[] to a String[] using hexadecimal. Does not catch
* any exceptions.
*/
public static String[] toStringArray(byte[] byteArray)
{
String[] toReturn = new String[byteArray.length];
for (int i = 0; i < toReturn.length; i++)
{
toReturn[i] = Integer.toString(byteArray[i] < 0 ? byteArray[i] + 256 : byteArray[i], 16);
}
return toReturn;
}
/**
* Renders an int array as a comma-delimited String for debug purposes.
*/
public static String toString(int[] intArray)
{
String[] strArray = toStringArray(intArray);
return toString(strArray, ",");
}
/**
* Renders an byte array as a comma-delimited String for debug purposes.
*/
public static String toString(byte[] intArray)
{
String[] strArray = toStringArray(intArray);
return toString(strArray, ",");
}
/**
* Merges and optionally sorts multiple String arrays.
*/
public static String[] arrayMerge(boolean sort, String[]... sourceArrays)
{
// Determine the total size of the new array.
int totalSize = 0;
if (sourceArrays != null)
{
for (String[] sourceArray : sourceArrays)
{
if (sourceArray != null)
{
totalSize += sourceArray.length;
}
}
}
// Create the new array.
String[] toReturn = new String[totalSize];
// Populate the new array.
int position = 0;
if (sourceArrays != null)
{
for (String[] sourceArray : sourceArrays)
{
if (sourceArray != null)
{
System.arraycopy(sourceArray, 0, toReturn, position,
sourceArray.length);
position += sourceArray.length;
}
}
}
// Sort if requested.
if (sort)
{
Arrays.sort(toReturn);
}
return toReturn;
}
/**
* Merges and optionally sorts multiple character arrays.
*/
public static char[] arrayMerge(boolean sort, char[]... sourceArrays)
{
// Determine the total size of the new array.
int totalSize = 0;
if (sourceArrays != null)
{
for (char[] sourceArray : sourceArrays)
{
if (sourceArray != null)
{
totalSize += sourceArray.length;
}
}
}
// Create the new array.
char[] toReturn = new char[totalSize];
// Populate the new array.
int position = 0;
if (sourceArrays != null)
{
for (char[] sourceArray : sourceArrays)
{
if (sourceArray != null)
{
System.arraycopy(sourceArray, 0, toReturn, position,
sourceArray.length);
position += sourceArray.length;
}
}
}
// Sort if requested.
if (sort)
{
Arrays.sort(toReturn);
}
return toReturn;
}
/**
* Generates a filled array of the provided value (all references to the
* same object!).
*/
public static String[] getFilledArray(String value, int size)
{
String[] toReturn = new String[size];
for (int i = 0; i < size; i++)
{
toReturn[i] = value;
}
return toReturn;
}
/**
* Generates a filled array of the provided value.
*/
public static boolean[] getFilledArray(boolean value, int size)
{
boolean[] toReturn = new boolean[size];
Arrays.fill(toReturn, value);
return toReturn;
}
/**
* Generates a filled array of the provided value.
*/
public static int[] getFilledArray(int value, int size)
{
int[] toReturn = new int[size];
Arrays.fill(toReturn, value);
return toReturn;
}
/**
* Creates a new Map that has been reduced to only the specified attributes,
* while also allowing the attributes to be renamed. This is useful in
* generating a Map for rendering as JavaScript/JSON from a Map that may
* contain elements that are not desired for rendering.
*
* originalAndNewNames is an interleaved String array of original
* attribute names followed by their new names. Any attributes in the
* input map that are not identified in this array will not be copied.
*
* Example usage: getReducedMap(userAttributes, "userFullname", "name")
*
* This would generate a new Map containing a single element, "name".
*
* @param originalAndNewNames an interleaved String array of original
* attribute names followed by their new names.
*/
public static Map getReducedMap(Map input,
String... originalAndNewNames)
{
if (originalAndNewNames.length % 2 != 0)
{
throw new IllegalArgumentException(
"The original and new names array must be of even length. Length of parameter: " + originalAndNewNames.length);
}
int length = originalAndNewNames.length / 2;
HashMap toReturn = new HashMap<>(length);
for (int i = 0; i < length; i++)
{
// Skip null original names.
if (originalAndNewNames[i * 2] != null)
{
E value = input.get(originalAndNewNames[i * 2]);
toReturn.put(originalAndNewNames[i * 2 + 1], value);
}
}
return toReturn;
}
/**
* Returns a new Collection that represents the intersection, i.e., the
* elements that are the same, between two collections. Implements the
* returned collection as an ArrayList.
*/
public static Collection getIntersection(Collection c1,
Collection c2)
{
Collection returnCollection = new ArrayList<>();
if ( (c1 != null)
&& (c2 != null)
)
{
for (E o : c1)
{
try
{
if (c2.contains(o))
{
returnCollection.add(o);
}
}
catch (Exception e)
{}
}
}
return returnCollection;
}
/**
* Creates a new list containing the given objects in natural order.
*/
public static > List getSorted(
Iterable objects)
{
return sort(toList(objects));
}
/**
* Creates a new list containing the given objects in the order defined by
* the given comparator
*/
public static List getSorted(Iterable objects,
Comparator comparator)
{
return sort(toList(objects), comparator);
}
/**
* Sorts and returns the given list.
*/
public static > List sort(List list)
{
Collections.sort(list);
return list;
}
/**
* Sorts and returns the given list using the given comparator.
*/
public static List sort(List list, Comparator comparator)
{
Collections.sort(list, comparator);
return list;
}
/**
* Reverses and returns the given list.
*/
public static List reverse(List list)
{
Collections.reverse(list);
return list;
}
/**
* Shuffles and returns the given list.
*/
public static List shuffle(List list)
{
Collections.shuffle(list);
return list;
}
/**
* You may not instantiate this class.
*/
private CollectionHelper()
{
// Does nothing.
}
} // End CollectionHelper.