What is the easiest/best/most correct way to iterate through the characters of a string in Java?

Question

StringTokenizer? Convert the String to a char[] and iterate over that? Something else?

Answer 1

If you need performance, then you must test on your environment. No other way.

Here example code:

int tmp = 0;
String s = new String(new byte[64*1024]);
{
    long st = System.nanoTime();
    for(int i = 0, n = s.length(); i < n; i++) {
        tmp += s.charAt(i);
    }
    st = System.nanoTime() - st;
    System.out.println("1 " + st);
}

{
    long st = System.nanoTime();
    char[] ch = s.toCharArray();
    for(int i = 0, n = ch.length; i < n; i++) {
        tmp += ch[i];
    }
    st = System.nanoTime() - st;
    System.out.println("2 " + st);
}
{
    long st = System.nanoTime();
    for(char c : s.toCharArray()) {
        tmp += c;
    }
    st = System.nanoTime() - st;
    System.out.println("3 " + st);
}
System.out.println("" + tmp);

On Java online I get:

1 10349420
2 526130
3 484200
0

On Android x86 API 17 I get:

1 9122107
2 13486911
3 12700778
0