liquibase.util.CollectionUtil Maven / Gradle / Ivy
package liquibase.util;
import java.util.*;
public class CollectionUtil {
public static Set> powerSet(Collection originalSet) {
Set> sets = new HashSet<>();
if (originalSet.isEmpty()) {
sets.add(new HashSet());
return sets;
}
List list = new ArrayList<>(originalSet);
T head = list.get(0);
Collection rest = list.subList(1, list.size());
for (Set set : powerSet(rest)) {
Set newSet = new HashSet<>();
newSet.add(head);
newSet.addAll(set);
sets.add(newSet);
sets.add(set);
}
return sets;
}
public static List> permutations(Map> parameterValues) {
List> list = new ArrayList<>();
if ((parameterValues == null) || parameterValues.isEmpty()) {
return list;
}
permute(new HashMap(), new ArrayList(parameterValues.keySet()), parameterValues, list);
return list;
}
private static void permute(Map basePermutation, List remainingKeys, Map> parameterValues, List> returnList) {
String thisKey = remainingKeys.get(0);
remainingKeys = remainingKeys.subList(1, remainingKeys.size());
for (T value : parameterValues.get(thisKey)) {
Map permutation = new HashMap<>(basePermutation);
permutation.put(thisKey, value);
if (remainingKeys.isEmpty()) {
returnList.add(permutation);
} else {
permute(permutation, remainingKeys, parameterValues, returnList);
}
}
}
}