no.mnemonic.commons.utilities.collections.SetUtils Maven / Gradle / Ivy
package no.mnemonic.commons.utilities.collections;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
public class SetUtils {
private SetUtils() {
}
/**
* Creates a set from its arguments.
*
* @param values Values to be added to the set.
* @param Type of value parameters.
* @return A set containing all values.
*/
@SafeVarargs
public static Set set(T... values) {
if (values == null) return new HashSet<>();
return new HashSet<>(Arrays.asList(values));
}
/**
* Creates a set from an iterator.
*
* @param iterator An iterator which values are added to the set.
* @param Type of iterator values.
* @return A set containing all values supplied by the given iterator.
*/
public static Set set(Iterator iterator) {
return set(iterator, v -> v);
}
/**
* Creates a set from another collection.
*
* @param collection A collection which values are added to the set.
* @param Type of collection values.
* @return A set containing all values contained in the given collection.
*/
public static Set set(Collection collection) {
if (collection == null) return new HashSet<>();
return new HashSet<>(collection);
}
/**
* Creates a set from its arguments using a mapping function converting all values.
*
* @param mapping A mapping function applied to all values.
* @param values Values to be added to the set.
* @param Type of value parameters before conversion.
* @param Type of values in the returned set after conversion.
* @return A set containing all values converted using the mapping function.
*/
@SafeVarargs
public static Set set(Function mapping, T... values) {
if (values == null) return new HashSet<>();
return set(Arrays.asList(values), mapping);
}
/**
* Creates a set from an iterator using a mapping function converting all values.
*
* @param iterator An iterator which values are added to the set.
* @param mapping A mapping function applied to all values.
* @param Type of iterator values before conversion.
* @param Type of values in the returned set after conversion.
* @return A set containing all values supplied by the given iterator and converted using the mapping function.
*/
public static Set set(Iterator iterator, Function mapping) {
if (mapping == null) throw new IllegalArgumentException("Mapping function not set!");
if (iterator == null) return new HashSet<>();
Set result = new HashSet<>();
iterator.forEachRemaining(o -> result.add(mapping.apply(o)));
return result;
}
/**
* Creates a set from another collection using a mapping function converting all values.
*
* @param collection A collection which values are added to the set.
* @param mapping A mapping function applied to all values.
* @param Type of collection values before conversion.
* @param Type of values in the returned set after conversion.
* @return A set containing all values contained in the given collection and converted using the mapping function.
*/
public static Set set(Collection collection, Function mapping) {
if (mapping == null) throw new IllegalArgumentException("Mapping function not set!");
if (collection == null) return new HashSet<>();
return collection.stream().map(mapping).collect(Collectors.toSet());
}
/**
* Adds an element to a set unless the element is null.
*
* A new set is created if the provided set is null.
*
* @param set Set to which the element will be added.
* @param element Element to add.
* @param Type of elements.
* @return Set including added element.
*/
public static Set addToSet(Set set, T element) {
if (set == null) set = new HashSet<>();
if (element == null) return set;
set.add(element);
return set;
}
/**
* Returns true if 'value' is among the argument list of 'values'.
*
* @param value Value to find.
* @param values Values to search through.
* @param Type of values.
* @return True if 'value' is present in the argument list.
*/
@SafeVarargs
public static boolean in(T value, T... values) {
if (set(values).isEmpty()) return false;
for (T element : values) {
if (Objects.equals(value, element)) return true;
}
return false;
}
/**
* Returns the intersection of multiple sets.
*
* The original sets are not altered.
*
* @param sets Multiple sets which will be intersected.
* @param Type of values.
* @return A set forming the intersection of the given sets.
*/
@SafeVarargs
public static Set intersection(Set... sets) {
if (sets == null) return new HashSet<>();
Set result = set(sets[0]);
for (int i = 1; i < sets.length; i++) {
result = intersectTwoSets(result, sets[i]);
}
return result;
}
/**
* Tests if multiple sets have common values, i.e. their intersection is not empty.
*
* @param sets Multiple sets to test for common values.
* @param Type of values.
* @return True if the given sets intersect.
*/
@SafeVarargs
public static boolean intersects(Set... sets) {
return !intersection(sets).isEmpty();
}
/**
* Returns the union of multiple sets.
*
* The original sets are not altered.
*
* @param sets Multiple sets which will be united.
* @param Type of values.
* @return A set forming the union of the given sets.
*/
@SafeVarargs
public static Set union(Set... sets) {
if (sets == null) return new HashSet<>();
Set result = new HashSet<>();
for (Set s : sets) {
if (s != null) result.addAll(s);
}
return result;
}
/**
* Applies add/remove modifications to a set.
*
* This operation permits adding to and removing from one set in a single operation.
*
* @param originSet Set to be modified.
* @param addSet Set containing elements to be added.
* @param removeSet Set containing elements to be removed.
* @param Type of values.
* @return Same instance of 'originSet' passed in after modification.
*/
public static Set modifySet(Set originSet, Set addSet, Set removeSet) {
if (originSet == null) return null;
if (!CollectionUtils.isEmpty(addSet)) originSet.addAll(addSet);
if (!CollectionUtils.isEmpty(removeSet)) originSet.removeAll(removeSet);
return originSet;
}
private static Set intersectTwoSets(Set a, Set b) {
if (a == null || b == null) return new HashSet<>();
Set result = new HashSet<>(a);
result.retainAll(b);
return result;
}
}