Backtracking

http://www.fas.harvard.edu/~cscie119/lectures/recursion.pdf

public void tail(int n) {
    if (n == 1)
        return;
    else
        System.out.println(n);

    tail(n - 1);
}

public void head(int n) {
    if (n == 0)
        return;
    else
        head(n - 1);
    System.out.println(n);
}