Compute Factorial in a Web Page

Factorial.java

package dew.demo.factorial;

import java.math.BigInteger;
import net.java.html.json.*;

@Model(targetId="", className="UI", properties={
  /** n is the number we want to compute factorial
  * when the Compute! button is pressed
  */
  @Property(name="n", type=int.class),
  /** array of computed results */
  @Property(name="results", type=String.class, array=true)
})
class ComputeFactorial {
  /** The actual method to compute factorial.
  * Shows we can use {@link BigInteger} in the
  * browser to get better numbers than JavaScript
  * offers by default.
  */
  public static String factorial(int n) {
    BigInteger r = BigInteger.valueOf(1);
    for (int i = 1; i <= n; i++) {
      r = r.multiply(BigInteger.valueOf(i));
    }
    return r.toString();
  }

  /** Called when a button Compute! is pressed.
  * Compute the result and add it to the result list.
  */
  @Function static void compute(UI ui) {
    ui.getResults().add(
      ui.getN() + "! = " + factorial(ui.getN())
    );
    ui.setN(ui.getN() + 1);
  }

  // initialize the UI  
  public static void main(String... args) {
    new UI().applyBindings();
  }
}

index.html

Factorial for: <input data-bind="value: n"></input> 

<button data-bind="click: compute" type="number">Compute!</button>

<h3>Your Results</h3>

<ul data-bind="foreach: results">
  <li data-bind="text:$data"></li>
</ul>

One can see the code in action at http://dew.apidesign.org/dew/#7337484