[java] Fix issue "Incompatible types for '-' operation" in the Javascript executor example
* ((JavascriptExecutor) driver).executeAsyncScript(
* "window.setTimeout(arguments[arguments.length - 1], 500);");
* System.out.println(
- * "Elapsed time: " + System.currentTimeMillis() - start);
+ * "Elapsed time: " + (System.currentTimeMillis() - start));
* }</pre>
*
* <p>
