Java Utililty Methods List Remove Duplicate

List<T> list = new ArrayList<T>();
for (T item : collection)
    if (!list.contains(item))
        list.add(item);
return list;

Set<T> s = new HashSet<>();
for (Iterator<T> iter = list.iterator(); iter.hasNext();) {
    T element = (T) iter.next();
    if (!s.add(element)) {
        iter.remove();
return list;
...

Collections.sort(list, comparator);
int j = 1;
for (int i = 1; i < list.size(); i++) {
    if (comparator.compare(list.get(j - 1), list.get(i)) != 0) {
        T object = list.get(i);
        list.set(j++, object);
if (j < list.size()) {
    list.subList(j, list.size()).clear();

for (ListIterator<V> it = lst.listIterator(); it.hasNext();) {
    int idx = it.nextIndex();
    V elem = it.next();
    if (idx < lst.size() - 1 && lst.subList(idx + 1, lst.size() - 1).contains(elem))
        it.remove();

Set<String> set = new HashSet<String>();
List<String> newList = new ArrayList<String>();
for (Iterator<String> iter = list.iterator(); iter.hasNext();) {
    String element = iter.next();
    if (set.add(element))
        newList.add(element);
list.clear();
...

Set<T> set = new LinkedHashSet<T>();
set.addAll(in);
if (set.size() == in.size())
    return in;
List<T> result = new ArrayList<T>();
for (T t : set)
    result.add(t);
return result;
...

if (list == null || list.isEmpty())
    return list;
T temp = null;
List<T> sublist;
for (int i = 0; i < list.size() - 1; i++) {
    temp = list.get(i);
    sublist = list.subList(i + 1, list.size());
    while (sublist.remove(temp)) {
...

if (isEmpty(list)) {
    return list;
List<T> result = new ArrayList<T>();
for (T e : list) {
    if (!result.contains(e)) {
        result.add(e);
return result;

Map<Integer, T> map = new HashMap<Integer, T>();
if (list == null)
    return null;
for (T t : list) {
    if (t == null)
        continue;
    map.put(t.hashCode(), t);
try {
    list.clear();
    list.addAll(map.values());
} catch (Exception e) {
return new ArrayList<T>(map.values());

if (strNames == null) {
    return null;
HashMap<String, Integer> seenBefore = new HashMap<String, Integer>(4);
List<String> results = new ArrayList<String>(strNames.size());
for (String str : strNames) {
    Integer lookup = seenBefore.get(str);
    if (lookup == null) {
...