Example: Reverse elements in an array

The idea is to use two pointers, one starts at the beginning, the other at the end, and to stop when they meet.

public void reverse(int[] v, int n) {
    int i = 0;
    int j = n-1;
    while(i<j) {
        swap(v, i , j);
        i++;
        j--;
    }
}

void swap(int[] v, int i, int j) {
    int tmp = v[i];
    v[i] = v[j];
    v[j] = tmp;
}