public static String[] swap(String s1, String s2) {
        String[] val = new String[2];
        val[0] = s2;
        val[1] = s1;
        return val;
    }

    public static void main(String[] args) {
        String s1 = "hello";
        String s2 = "bye";
        String[] s = swap(s1, s2);
        System.out.println(s[0] + " " + s[1]); // bye hello
    }