Java Utililty Methods Comma Separated List

StringBuilder sb = new StringBuilder();
String sep = "";
for (String item : items) {
    sb.append(sep);
    sb.append(item);
    sep = ",";
return sb.toString();
...

String mainString = "";
for (String string : strings)
    mainString += "," + string;
mainString.replaceFirst(",", "");
return mainString;

List<String> list = new ArrayList<String>();
if (csvListStr != null && csvListStr.trim().length() > 0) {
    String[] ignoreListArr = csvListStr.split(",");
    for (int i = 0; i < ignoreListArr.length; i++) {
        list.add(ignoreListArr[i]);
return list;
...

if (str == null) {
    return new ArrayList<>();
return Arrays.asList(str.split("\\s*,\\s*"));

if (strValue != null && !strValue.isEmpty()) {
    return Arrays.asList(strValue.split("\\s*,\\s*"));
return new ArrayList<>();

List<String> retList = null;
if (commSepLine != null) {
    String[] calls = commSepLine.split(",");
    if (calls != null) {
        retList = new ArrayList<String>();
        for (String call : calls) {
            retList.add(call.trim());
return retList;

return Arrays.asList(inputString.split("\\s*,\\s*"));

List result = null;
if (s != null) {
    result = new ArrayList();
    String[] valueArray = s.split(",");
    for (int i = 0; i < valueArray.length; i++) {
        String value = valueArray[i];
        if (value != null) {
            value = value.trim();
...

String s = "";
if (list != null) {
    for (Long l : list) {
        if (s.length() > 0)
            s += ",";
        s += "" + l;
return s;

List<String> stringValues = new ArrayList<>();
if (valuesCommaSeparated != null) {
    for (String value : valuesCommaSeparated.split(",")) {
        if (!isBlank(value)) {
            stringValues.add(value);
return stringValues;