日期相关

Date类

new Date()
Thu Apr 27 10:35:17 CST 2023

Calendar类

//获取当前时间的后n天
Calendar ca=Calendar.getInstance();
ca.setTime(new Date());
ca.add(Calendar.Date,n);  //天
ca.add(Calendar.Hour,n)   //小时
new Date=ca.getTime();

SimpleDateFormat类

String pattern="yyyymmdd"
SimpleDateFormat s=new SimpleDateFormat(pattern);
String newTime=s.format(new Date());