Java Utililty Methods List Concatenate

List<A> result = new ArrayList<>(lista);
result.addAll(listb);
return Collections.unmodifiableList(result);

StringBuilder sb = new StringBuilder();
for (int i = 0; i < items.size(); i++) {
    sb.append(quotation + items.get(i) + quotation);
    if (i < items.size() - 1) {
        sb.append(separation);
return sb.toString();
...

StringBuilder sb = new StringBuilder();
for (String item : items) {
    sb.append(item).append(separator);
if (sb.length() > 0) {
    return sb.substring(0, sb.length() - separator.length());
} else {
    return null;
...

StringBuilder sb = new StringBuilder();
String sep = "";
for (String s : strings) {
    sb.append(sep).append(s);
    sep = separator;
return sb.toString();

StringBuilder sb = new StringBuilder(tokens.size() * 10);
int size = tokens.size();
for (int i = 0; i < size; i++) {
    sb.append(tokens.get(i));
    if (i < size - 1) {
        sb.append(TOKEN_SEPARATER);
return sb.toString();

StringBuilder sb = new StringBuilder();
for (int i = 0; i < words.size(); i++)
    sb.append(i > 0 ? "@" : "").append(words.get(i));
return sb.toString();

List<String> c = new ArrayList<String>();
for (List<String> l : lists) {
    c.addAll(l);
return c.toArray(new String[c.size()]);

Iterator<StringBuilder> it = lista.iterator();
while (it.hasNext()) {
    destino.append(it.next());
    if (it.hasNext()) {
        destino.append(sep);

List<T> result = new ArrayList<>(a.size() + b.size());
result.addAll(a);
result.addAll(b);
return result;

if (isEmpty(collection1)) {
    return collection2;
if (isEmpty(collection2)) {
    return collection1;
collection1.addAll(collection2);
return collection1;
...