Can I get an explanation on how this code works???

public static void main(String[] args)
    {
        String mnMeth = "Main method: passing %s to reverse() Start: %s - end: %s";
        String line = "**************************************************************************************";
        String str = "abcdef";
        char[] A = str.toCharArray();
        int offset=3;
        int len = A.length;
        offset %= len;
        System.out.println(String.format(mnMeth,Arrays.toString(A),0,len - offset - 1));
        reverse(A, 0, len - offset - 1);
        System.out.println(line);
        System.out.println(String.format(mnMeth,Arrays.toString(A),len - offset,len - 1));
        reverse(A, len - offset, len - 1);
        System.out.println(line);
        System.out.println(String.format(mnMeth,Arrays.toString(A),0,len - 1));
        reverse(A, 0, len - 1);
        System.out.println(line);
        System.out.println("\n"+Arrays.toString(A));
    }

    private static void reverse(char[] str, int start, int end) {
        System.out.println("\tInside reverse() method");
        while (start < end) {
            System.out.println("\tArray = " + Arrays.toString(str));
            System.out.println("\tSwapping \'"+ str[start] + "\' at index " + start + " with \'" + str[end] + "\' at index " + end);
            char temp = str[start];
            str[start] = str[end];
            str[end] = temp;
            start++;
            end--;
        }
        System.out.println("\tArray = " + Arrays.toString(str));
        System.out.println("\tReturning to main()");
    }