Counting button clicks in Java with low level JavaScript interaction

Counting.java

package dew.demo.lowlevel;

import net.java.html.js.JavaScriptBody;

final class Java2JsAndBack implements Runnable {
  private int cnt = 0;  
  
  @Override public void run() {
    String msg = "I was pressed";
    if (++cnt > 1) {
      msg += " " + cnt + " times";
    }
    changeText("button", msg);
  }
  
//
// Java/JS bridge utility methods. Visit
// http://bits.netbeans.org/html+java/1.3/net/java/html/js/package-summary.html
// to learn how to use the @JavaScriptBody annotation
//

  @JavaScriptBody(args = { "id", "text" }, body =
    "var e = window.document.getElementById(id);\n" +
    "e.innerHTML = text;"
  ) 
  public static native void changeText(String id, String text);
  
  @JavaScriptBody(args = { "id", "r" }, 
    javacall = true, body = 
    "var e = window.document.getElementById(id);\n" +
    "e.onclick = function() {" +
    "  r.@java.lang.Runnable::run()();" +
    "};"
  )                  
  public static native void onclick(String id, Runnable r);

  //
  // initialization
  // 
  
  static {
    Java2JsAndBack handler = new Java2JsAndBack();
    onclick("button", handler);
  }
}

index.html

<button id="button">Press me!</button>

See the live snippet by visiting its DEW at http://dew.apidesign.org/dew/#7102188