import structure5.*;

public class GenericReverser {
    /**
     * Reverses the order of elements in a Vector,
     * in place.
     *
     * @param v The Vector to be reversed.
     */
    public static <T> void reverse(Vector<T> v) {
        // swap elements at i and j;
        // i is an element on the left,
        // j is an element on the right.
        for (int i = 0; i < v.size() / 2; i++) {            
            int j = v.size() - i - 1;
            T tmp = v.get(i);
            // uncomment to observe swaps
            //System.out.println("Swap i = " + i + " and j = " + j);
            v.setElementAt(v.get(j), i);
            v.setElementAt(tmp, j);
        }
    }
    
    public static void main(String[] args) {
        // an array
        Vector<Integer> v = new Vector<Integer>();
        v.add(1);
        v.add(2);
        v.add(3);
        v.add(4);

        // print it
        System.out.println(v);

        // reverse it ("in place")
        reverse(v);

        // print it again
        System.out.println(v);
    }
}