java int型日期转为date或特定格式

Calendar c=Calendar.getInstance();
int seconds = 1514871613;//数据库中提取的数据
long millions=new Long(seconds).longValue()*1000;
c.setTimeInMillis(millions);
System.out.println(""+c.getTime());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = sdf.format(c.getTime());
System.out.println(dateString);