Java Utililty Methods List Merge

List<T> mergedList = new ArrayList<T>(countCollectionsSize(cols));
for (Collection<T> oneList : cols) {
    if (oneList == null)
        continue;
    mergedList.addAll(oneList);
return mergedList;

if (x.size() != y.size())
    throw new IllegalArgumentException(
            "Sample sizes must be the same for each data applyTransformToDestination.");
List<Double> ret = new ArrayList<>();
for (int i = 0; i < x.size(); i++) {
    ret.add(x.get(i));
    ret.add(y.get(i));
return ret;

if (lstMain == null || lstData == null || lstData.size() == 0 || lstKey == null || lstKey.size() == 0) {
    return;
for (int index1 = 0, n = lstMain.size(); index1 < n; index1++) {
    Map mapMain = (Map) lstMain.get(index1);
    Map keyValue = new HashMap();
    for (int index2 = 0, m = lstKey.size(); index2 < m; index2++) {
        Object key = lstKey.get(index2);
...

List<T> merged = new AbstractList<T>() {
    @Override
    public T get(int index) {
        if (index < left.size())
            return left.get(index);
        else if (index - left.size() < right.size())
            return right.get(index - left.size());
        else
...

StringBuilder errorMsg = new StringBuilder();
for (String msg : errorMsgs) {
    errorMsg.append(msg);
    errorMsg.append(", ");
return errorMsg.substring(0, errorMsg.length() - 2);

Exception exception = new Exception();
return exception;

List<String> localExcludes = Arrays.asList(localClassExcludes);
List<String> superExcludes = Arrays.asList(superClassExcludes);
List<String> mergedExcludes = new ArrayList<String>(localExcludes);
mergedExcludes.addAll(superExcludes);
return mergedExcludes.toArray(new String[] {});

for (String f : parentFilters) {
    if (!childFilters.contains(f)) {
        childFilters.add(f);

if (hierachicalDimensions.size() == 0) {
    return flatDimensions;
if (flatDimensions.size() == 0) {
    return hierachicalDimensions;
Collection<List<Boolean>> result = new ArrayList<>(hierachicalDimensions.size() * flatDimensions.size());
hierachicalDimensions.forEach(hierarchicalCombination -> {
...

List<String> ps = new ArrayList<>();
for (String str : strs) {
    ps.add(mergeIdAndString(accountId, workspaceId, str));
return ps;