Code architecture

[diamonddragon]

Have four different code examples with same output result.
Question is, which example is better?

    public static void main (String[] args) {
        String prefix = prefix("xxx00", "xxxxxxxxxx");
    }
    
    public static String prefix(String s1, String s2) {
        int min = s1.length() < s2.length() ? s1.length() : s2.length();
        String prefix = "";
        int i = 0;
        while (i < min && s1.charAt(i) == s2.charAt(i)) {           
            prefix += s1.charAt(i++);
        }
        return prefix;
    }

or:

        while (i < min) {           
            if (s1.charAt(i) == s2.charAt(i))
                prefix += s1.charAt(i);
            i++;
        }

or:

        for (int i = 0; i < min; i++)
            if (s1.charAt(i) == s2.charAt(i))
                prefix += s1.charAt(i);

or:

        for (int i = 0; i < min && s1.charAt(i) == s2.charAt(i); i++)
            prefix += s1.charAt(i);

or?

[JosAH]

I'd get the prefix after the loop has finished; it doesn't matter much for your small examples but if the common prefix happens to be large, a lot of Strings have been created and thrown away during those loops.

kind regards,

Jos

[diamonddragon]

Do You mean each time I concatenate String object, it is actually new String object, because of String immutability?

So, is something like this best solution?

        int i;
        for (i = 0; i < min && s1.charAt(i) == s2.charAt(i); i++);
        prefix = s1.substring(0, i);

[JosAH]

Do You mean each time I concatenate String object, it is actually new String object, because of String immutability?

So, is something like this best solution?

        int i;
        for (i = 0; i < min && s1.charAt(i) == s2.charAt(i); i++);
        prefix = s1.substring(0, i);

Yup, that's much better (big-Oh wise that is).

kind regards,

Jos