java常见日期格式转换以及日期的获取

2018-09-10 01:03:22来源：博客园阅读 ()

package com.test.TestBoot.SingleModel;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Test {
   public static void main(String[] args) {

       /**
       * Date 转 String
       */
        Date date = new Date();
        String dateStr = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(date);
        System.out.println(dateStr);


        /**
       *String 转 Date
       */
        String ss = "2016-10-24 21:59:06";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
           Date d = sdf.parse(ss);
           System.out.println(d);
       } catch (ParseException e) {
           e.printStackTrace();
       }

        /**
         * 本月第一天
         */
        Calendar monthca = Calendar.getInstance();
       monthca.add(Calendar.MONTH, 0);
       monthca.set(Calendar.DAY_OF_MONTH,1);
       String monthfirstDay = sdf.format(monthca.getTime());   //本月第一天
        System.out.println(monthfirstDay);

         /**
         * 本月最后一天
         */
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DATE));
        String monthlastday = sdf.format(calendar.getTime());   //本月最后一天
        System.out.println(monthlastday);

       /**
         * 昨天
         */
        Calendar startca = Calendar.getInstance();    // 得到一个Calendar的实例
       startca.setTime(new Date());                   // 设置时间为当前时间
       startca.add(Calendar.DATE, -1);                // 日期减1
        Date sDate = startca.getTime();               //前一天的时间
        SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd");
        String starttime = sd.format(sDate);                   //前一天的时间(昨天)
        System.out.println(starttime);

     /**
         * 上个月第一天
         */
        Calendar lastmonthfirst = Calendar.getInstance();
        lastmonthfirst.add(Calendar.MONTH, -1);
        lastmonthfirst.set(Calendar.DAY_OF_MONTH, 1);
        String lastmonthfirstday = sd.format(lastmonthfirst.getTime());   //上个月第一天
        System.out.println(lastmonthfirstday);

        /**
         * 上个月最后一天
         */
        Calendar lastmonthlast = Calendar.getInstance();
        lastmonthlast.set(Calendar.DAY_OF_MONTH, 1);
        lastmonthlast.add(Calendar.DATE, -1);
        String lastmonthlastday = sd.format(lastmonthlast.getTime());       //上个月最后一天
        System.out.println(lastmonthlastday);

   }

}