docs/Factorial.java

import java.io.*;

public class Factorial {
  private static BufferedReader in = new BufferedReader(new
                                InputStreamReader(System.in));

  public static final int fac(int n) {
    return(n == 0)? 1 : n * fac(n - 1);
  }

  public static final int readInt() {
    int n = 4711;

    try {
      System.out.print("Please enter a number> ");
      n = Integer.parseInt(in.readLine());
    }
    catch(IOException e1) { System.err.println(e1); }
    catch(NumberFormatException e2) { System.err.println(e2); }

    return n;
  }

  public static void main(String[] args) {
    int n = readInt();
    System.out.println("Factorial of " + n + " is " + fac(n));
  }
}