Java Utililty Methods String from List

StringBuffer sb = new StringBuffer();
for (int i = 0; i < strList.size(); i++) {
    String s = (String) strList.get(i);
    if (i != 0) {
        sb.append(delim);
    sb.append(s);
return sb.toString();

if (strs == null)
    strs = Collections.emptyList();
List<byte[]> skeys = new ArrayList<byte[]>(strs.size());
for (String s : strs) {
    skeys.add(s.getBytes());
return skeys;

boolean[][] matriz = null;
for (int i = 0; i < linhas.size(); i++) {
    String[] nos = linhas.get(i).split(SEPARADOR);
    if (matriz == null) {
        matriz = new boolean[nos.length][linhas.size()];
    for (int j = 0; j < nos.length; j++) {
        matriz[j][i] = Boolean.parseBoolean(nos[j]);
...