Java Utililty Methods Random String

StringBuffer sb = new StringBuffer();
int n = r.nextInt(12);
for (int i = 0; i < n; i++) {
    sb.append((char) (r.nextInt(26) + 'a'));
return sb.toString();

StringBuilder sb = new StringBuilder();
sb.append(System.currentTimeMillis());
sb.append(new Random().nextInt(10000));
return sb.toString();

String[] baseString = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f", "g",
        "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "A",
        "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U",
        "V", "W", "X", "Y", "Z" };
Random random = new Random();
int length = baseString.length;
String randomString = "";
for (int i = 0; i < length; i++) {
...

Random randGen = null;
char[] numbersAndLetters = null;
Object initLock = new Object();
if (length < 1) {
    return null;
if (randGen == null) {
    synchronized (initLock) {
...

Random rnd = new Random(System.currentTimeMillis());
StringBuffer buf = new StringBuffer();
for (int i = 0; i < length; i++) {
    int val = rnd.nextInt(chars.length());
    buf.append(chars.charAt(val));
return buf.toString();

StringBuffer sbf = new StringBuffer();
Random rand = new Random();
int charSize = characters.length();
for (int i = 0; i < length; i++) {
    sbf.append(characters.charAt(rand.nextInt(charSize)));
return sbf.toString();

String s = "";
Random random = new Random();
for (int i = 0; i < n; i++) {
    s = s + random.nextInt(10);
return s;

String d = "abcdfghijklmnopqrtuvwxyz";
Random rand = new Random();
int i = 0;
int n = 0;
String f = "";
while (i < qty) {
    n = rand.nextInt(24 - 0 + 1) + 0;
    f += d.substring(n, n + 1);
...

if (null == src || "".equals(src)) {
    return "";
Random random = new Random();
return String.valueOf(src.charAt(random.nextInt(src.length())));

return bytes2Hex(getRandomBytes());