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package pl.jalokim.utils.collection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import static java.util.Arrays.asList;
import static java.util.Collections.unmodifiableList;
/**
* Some utils methods for collections.
*/
public final class CollectionUtils {
private CollectionUtils() {
}
/**
* check that given index is last in certain list.
*
* @param list list to check.
* @param index index to check
* @return boolean value.
*/
public static boolean isLastIndex(List list, int index) {
return getLastIndex(list) == index;
}
/**
* check that given index is last in certain array.
*
* @param array list to check.
* @param index index to check
* @return boolean value.
*/
public static boolean isLastIndex(Object[] array, int index) {
return getLastIndex(array) == index;
}
/**
* It returns last index from list.
*
* @param list for get last index.
* @return last index for certain list.
*/
public static int getLastIndex(Collection list) {
return list.size() - 1;
}
/**
* It returns last index from array.
*
* @param array for get last index.
* @return last index for certain array.
*/
public static int getLastIndex(Object[] array) {
return array.length - 1;
}
/**
* This method get some collection and filter expected elements and put them to new set.
*
* @param collection source collection.
* @param filter predicate for filter.
* @param generic type for collection and predicate.
* @return new Set of filtered element from source collection.
*/
public static Set filterToSet(Collection collection, Predicate filter) {
return collection.stream()
.filter(filter)
.collect(Collectors.toSet());
}
/**
* This method return new Set with mapped values from source collection.
*
* @param collection source elements.
* @param mapFunc function for map from collection to new Set with another types.
* @param type for source collection.
* @param type for result Set.
* @return new Set with another type elements than source elements type.
*/
public static Set mapToSet(Collection collection, Function mapFunc) {
return collection.stream()
.map(mapFunc)
.collect(Collectors.toSet());
}
/**
* This method return new Set with mapped values from source collection.
* But after map it can filter them by last method argument.
*
* @param collection source elements.
* @param mapFunc function for map from collection to new Set with another types.
* @param filter predicate for mapped elements.
* @param type for source collection.
* @param type for result Set.
* @return set with another type of filtered elements than from source.
*/
public static Set mapToSet(Collection collection,
Function mapFunc,
Predicate filter) {
return collection.stream()
.map(mapFunc)
.filter(filter)
.collect(Collectors.toSet());
}
/**
* This method get some collection and filter expected elements and map them to new type and put results to new Set.
*
* @param collection source collection.
* @param filter predicate for filter by source elements type.
* @param mapFunc map to new type filtered result.
* @param type for source collection.
* @param type for result Set.
* @return Set with filtered source and another types than source collection.
*/
public static Set filterToSet(Collection collection,
Predicate filter,
Function mapFunc) {
return collection.stream()
.filter(filter)
.map(mapFunc)
.collect(Collectors.toSet());
}
/**
* This method return new List with mapped values from source collection.
*
* @param collection source elements.
* @param mapFunc function for map from collection to new List with another types.
* @param type for source collection.
* @param type for result List.
* @return new List with another type elements than source elements type.
*/
public static List mapToList(Collection collection, Function mapFunc) {
return collection.stream()
.map(mapFunc)
.collect(Collectors.toList());
}
/**
* This method get some collection and filter expected elements and put them to new List.
*
* @param collection source collection.
* @param filter predicate for filter.
* @param generic type for collection and predicate.
* @return new List of filtered element from source collection.
*/
public static List filterToList(Collection collection, Predicate filter) {
return collection.stream()
.filter(filter)
.collect(Collectors.toList());
}
/**
* This method return new List with mapped values from source collection.
* But after map it can filter them by last method argument.
*
* @param collection source elements.
* @param mapFunc function for map from collection to new List with another types.
* @param filter predicate for mapped elements.
* @param type for source collection.
* @param type for result List.
* @return new List with another type of filtered elements than source elements type.
*/
public static List mapToList(Collection collection,
Function mapFunc,
Predicate filter) {
return collection.stream()
.map(mapFunc)
.filter(filter)
.collect(Collectors.toList());
}
/**
* This method get some collection and filter expected elements and map them to new type and put results to new List.
*
* @param collection source collection.
* @param filter predicate for filter by source elements type.
* @param mapFunc map to new type filtered result.
* @param type for source collection.
* @param type for result List.
* @return new List with filtered source and another types than source collection.
*/
public static List filterToList(Collection collection,
Predicate filter,
Function mapFunc) {
return collection.stream()
.filter(filter)
.map(mapFunc)
.collect(Collectors.toList());
}
/**
* This method return new List with mapped values from source array.
*
* @param mapFunc function for map from collection to new List with another types.
* @param array source elements.
* @param type for source array.
* @param type for result List.
* @return new List with another type elements than source elements type.
*/
public static List mapToList(Function mapFunc, T... array) {
return mapToList(asList(array), mapFunc);
}
/**
* This method return new List with mapped values from source array.
* But after map it can filter them by second method argument.
*
* @param mapFunc function for map from collection to new List with another types.
* @param predicate predicate for filter.
* @param array source elements.
* @param type for source array.
* @param type for result List.
* @return new List with another type elements than source elements type.
*/
public static List mapToList(Function mapFunc, Predicate predicate, T... array) {
return mapToList(asList(array), mapFunc, predicate);
}
/**
* This method get some collection and filter expected elements and put them to new List.
*
* @param predicate predicate for filter.
* @param array source collection.
* @param generic type for collection and predicate.
* @return new List of filtered element from source array.
*/
public static List filterToList(Predicate predicate, T... array) {
return filterToList(asList(array), predicate);
}
/**
* This method get some array and filter expected elements and map them to new type and put results to new List.
*
* @param predicate predicate for filter by source elements type.
* @param mapFunc map to new type filtered result.
* @param array source array.
* @param type for source array.
* @param type for result List.
* @return new List with filtered source and another types than source array.
*/
public static List filterToList(Predicate predicate, Function mapFunc, T... array) {
return filterToList(asList(array), predicate, mapFunc);
}
/**
* It get list and sort elements but not change source list.
*
* @param list to sort.
* @param generic type in list.
* @return returns copy of source list but with sorted values.
*/
public static > List sortAsNewList(Collection list) {
List copyList = new ArrayList<>(list);
Collections.sort(copyList);
return copyList;
}
/**
* Swap element in copy of sourceList and returns it.
*
* @param sourceList source for swap.
* @param indexToSwap index element to swap in copy of source list
* @param newValue new value in certain index.
* @param generic type for list.
* @return copy of source list with swapped value.
*/
public static List swapElementsAsNewList(List sourceList, int indexToSwap, T newValue) {
List copyList = new ArrayList<>(sourceList);
copyList.set(indexToSwap, newValue);
return copyList;
}
/**
* It returns first element from list if present.
*
* @param list as source
* @param generic type
* @return returns first element if present.
*/
public static T getFirst(List list) {
if (list.isEmpty()) {
throw new CollectionUtilsException("cannot get first element from empty list: " + list);
}
return list.get(0);
}
/**
* It returns last element from list if present.
*
* @param list as source
* @param generic type
* @return returns last element if present.
*/
public static T getLast(List list) {
if (list.isEmpty()) {
throw new CollectionUtilsException("cannot get last element from empty list: " + list);
}
return list.get(list.size() - 1);
}
/**
* It add to list if is not present already.
*
* @param list where will be added element.
* @param element to add.
* @param generic type of list and tried add element.
* @return return true when element was added.
*/
public static boolean addWhenNotExist(List list, T element) {
if (!list.contains(element)) {
return list.add(element);
}
return false;
}
/**
* It return true when provided collections have the same elements. Order or elements is not important here.
*
* @param first collection
* @param second collection
* @param generic type of collections.
* @return true when has the same elements.
*/
public static > boolean hasTheSameElements(Collection first, Collection second) {
return new HashSet<>(first).equals(new HashSet<>(second));
}
/**
* It returns true when list is null or empty.
*
* @param list to verify.
* @param generic type.
* @return boolean value.
*/
public static boolean isEmpty(List list) {
return list == null || list.isEmpty();
}
/**
* It returns true only when list is not null, and if not empty.
*
* @param list to verify.
* @param generic type.
* @return boolean value.
*/
public static boolean isNotEmpty(List list) {
return !isEmpty(list);
}
/**
* It return intersection for two given collections.
*
* @param first collection.
* @param second collection.
* @param generic type.
* @return return intersected elements.
*/
public static List intersection(Collection first, Collection second) {
List list = new ArrayList<>();
for (E element : first) {
if (second.contains(element)) {
list.add(element);
}
}
return unmodifiableList(list);
}
}
