JAVA get the current date increase of one or more days

SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
Calendar c = Calendar.getInstance();
System.out.println("当前日期:"+sf.format(c.getTime()));
c.add(Calendar.DAY_OF_MONTH, 1);
System.out.println("增加一天后日期:"+sf.format(c.getTime()));
//打印结果
//当前日期：         2013-06-18
//增加一天后日期 ：   2013-06-19