哪个更快？ 在分割字符串上

Question

Which onr is faster and Why?

StringTokenizer st = new StringTokenizer(br.readLine(), "", false);
String[] s = new String[st.countTokens()];
int a = 0;
while (st.hasMoreTokens())
    s[a++] = st.nextToken();

or

String[] s = br.readLine().split("");