设置时间四种方法

1、通过Date类来获取当前时间

Date day=new Date();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(df.format(day));
2、通过System类中的currentTimeMillis方法来获取当前时间

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
System.out.println(df.format(System.currentTimeMillis()));
3、通过Calendar类来获取当前时间

Calendar c = Calendar.getInstance();//可以对每个时间域单独修改
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int date = c.get(Calendar.DATE);
int hour = c.get(Calendar.HOUR_OF_DAY);
int minute = c.get(Calendar.MINUTE);
int second = c.get(Calendar.SECOND);
System.out.println(year + "/" + month + "/" + date +
" " +hour + ":" +minute + ":" + second);
4、通过Date类来获取当前时间 

Date date = new Date();
String year = String.format("%tY", date);
String month = String.format("%tB", date);
String day = String.format("%te", date);
System.out.println("今天是："+year+"-"+month+"-"+day);