Java Utililty Methods List Uniqne Item

if (array == null)
    throw new NullPointerException("Not initizalize array");
List<E> uniq = new ArrayList<E>();
HashMap<E, Boolean> visited = new HashMap<E, Boolean>();
for (E s : array) {
    if (!visited.containsKey(s)) {
        uniq.add(s);
        visited.put(s, true);
...

if (entities.isEmpty()) {
    return null;
if (entities.size() == 1) {
    return entities.get(0);
throw new IllegalArgumentException(
        "wanted to get a unique entity from a list that contains more than one...");
...

if (list.size() < 2) {
    return list;
List<T> sorted = new LinkedList<T>(list);
Collections.sort(sorted);
T current = sorted.get(sorted.size() - 1);
for (int i = sorted.size() - 1; i > 0; i--) {
    T previous = sorted.get(i - 1);
...

list)
Remove all duplicated entries.

ArrayList<P> uniqueList = new ArrayList<>();
for (P item : list) {
    if (uniqueList.contains(item)) {
        continue;
    uniqueList.add(item);
return uniqueList;
...

if (list == null) {
    return null;
List<T> unique = new ArrayList<T>(list.size());
for (T next : list) {
    if (!unique.contains(next)) {
        unique.add(next);
return unique;

if (list2 != null) {
    for (String fromList2 : list2) {
        if (!list1.contains(fromList2) && (!"#".equals(fromList2))) {
            list1.add(fromList2);
return list1;
...

for (Object mac1 : macs) {
    final String mac = (String) mac1;
    if (attempt.equals(mac)) {
        return false;
return true;