Java Utililty Methods List Concatenate

long ret = 0;
int size = instructionbytes.size();
for (int i = size - 1; i > (size - 1 - num); i--) {
    ret = ret << 8;
    ret += (0x00000000000000FFL & instructionbytes.get(i));
return ret;

int size = 0;
for (Collection<T> list : lists) {
    size += list.size();
List<T> result = new ArrayList<T>(size);
for (Collection<T> list : lists) {
    result.addAll(list);
return result;

List<T> result = new ArrayList<>(list1);
result.addAll(list2);
return result;

if (result == null || result.length == 0)
    return result;
int pos = 0;
for (final byte[] buffer : buffers) {
    System.arraycopy(buffer, 0, result, pos, buffer.length);
    pos += buffer.length;
return result;
...

ArrayList<T> al = new ArrayList<T>();
for (Collection<? extends T> list : lists)
    if (list != null)
        al.addAll(list);
return al;

if (list1 == null || list2 == null)
    throw new NullPointerException("Not initizalized lists");
List<E> concat = new ArrayList<E>(list1.size() + list2.size());
concat.addAll(list1);
concat.addAll(list2);
return concat;

if (list.size() > 0) {
    final StringBuilder result = new StringBuilder();
    Iterator iter = list.iterator();
    while (iter.hasNext()) {
        result.append(iter.next().toString());
        if (iter.hasNext()) {
            result.append(".");
    return result.toString();
} else {
    return "";

List<T> list = new ArrayList<>();
list.addAll(l1);
list.addAll(l2);
return list;

if (list1 == null && list2 == null) {
    return null;
final List<T> result = new ArrayList<>();
if (list1 != null)
    result.addAll(list1);
if (list2 != null)
    result.addAll(list2);
...

String ret = list.get(0) + "";
for (int i = 1; i < list.size(); i++) {
    ret = ret + delim + list.get(i);
return ret;