public PayloadBuilder badge(final int badge) {
        aps.put("badge", badge);
        return this;
    }
Sets the notification badge to be displayed next to the
application icon.

The passed value is the value that should be displayed
(it will be added to the previous badge number), and
a badge of 0 clears the badge indicator.

@param badge the badge number to be displayed
@return  this
src/main/java/com/notnoop/apns/PayloadBuilder.java