code: @Override
      public void setValue(Boolean value, boolean fireEvents) {
          if (value == null) {
              value = Boolean.FALSE;
          }
  
          Boolean oldValue = getValue();
          inputElem.setChecked(value);
          inputElem.setDefaultChecked(value);
          if (value.equals(oldValue)) {
              return;
          }
          if (fireEvents) {
              ValueChangeEvent.fire(this, value);
          }
      }
docs: Checks or unchecks the check box, firing {@link ValueChangeEvent} if
  appropriate.
  <p>
  Note that this <em>does not</em> set the value property of the checkbox
  input element wrapped by this widget. For access to that property, see
  {@link #setFormValue(String)}
  
  @param value      true to check, false to uncheck; null value implies false
  @param fireEvents If true, and value has changed, fire a
  {@link ValueChangeEvent}