一. 获取当前系统时间和日期并格式化输出:
import java.util.Date;
import java.text.SimpleDateFormat;
public class NowString {
public static void main(String[] args) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//设置日期格式
System.out.println(df.format(new Date()));// new Date()为获取当前系统时间
}
}
二、获取昨天时间
取昨天的日期,本想的截出来日期减一就好了。又一想不对,如果今天是一号怎么办?
现有两个办法
1:Date as = new Date(new Date().getTime()-24*60*60*1000);
SimpleDateFormat matter1 = new SimpleDateFormat("yyyy-MM-dd");
String time = matter1.format(as);
System.out.println(time);
取出数字型的时间 再减去24*60*60*1000,就得到昨天的时间了;
这个有点过时了!
2:Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE, -1);
String yesterday = new SimpleDateFormat( "yyyy-MM-dd ").format(cal.getTime());
System.out.println(yesterday);
这个方法很方便,年月日都可以随心所欲的变!
看下面的程序
package com.yiibai;
import java.util.Calendar;
public class CalendarDemo {
public static void main(String[] args) {
// create a calendar
Calendar cal = Calendar.getInstance()
// print current date
System.out.println("The current date is : " + cal.getTime());
// add 20 days to the calendar
cal.add(Calendar.DATE, 20);
System.out.println("20 days later: " + cal.getTime());
// subtract 2 months from the calendar
cal.add(Calendar.MONTH, -2);
System.out.println("2 months ago: " + cal.getTime());
// subtract 5 year from the calendar
cal.add(Calendar.YEAR, -5);
System.out.println("5 years ago: " + cal.getTime());
}
}
让我们来编译和运行上面的程序,这将产生以下结果:
The current date is : Thu Apr 26 02:13:28 EEST 2012
20 days later: Wed May 16 02:13:28 EEST 2012
2 months ago: Fri Mar 16 02:13:28 EET 2012
5 years ago: Fri Mar 16 02:13:28 EET 2007