package com.test.packager;

 import java.text.ParseException;

 import java.text.SimpleDateFormat;

 import java.util.Calendar;

 public class Test {

   private static String firstDay;

   private static String lastDay;

     public static void main(String[] args) {

         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); 

         //获取前月的第一天

         Calendar   cal_1=Calendar.getInstance();//获取当前日期

         cal_1.add(Calendar.MONTH, -1);

         cal_1.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天

         firstDay = format.format(cal_1.getTime());

         System.out.println("-----1------firstDay:"+firstDay);

         //获取前月的最后一天

         Calendar cale = Calendar.getInstance();

         cale.set(Calendar.DAY_OF_MONTH,0);//设置为1号,当前日期既为本月第一天

         lastDay = format.format(cale.getTime());

         System.out.println("-----2------lastDay:"+lastDay);

         //获取当前月第一天：

         Calendar c = Calendar.getInstance();

         c.add(Calendar.MONTH, 0);

         c.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天

         String first = format.format(c.getTime());

         System.out.println("===============first:"+first);

         //获取当前月最后一天

         Calendar ca = Calendar.getInstance();

         ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));

         String last = format.format(ca.getTime());

         System.out.println("===============last:"+last);

     }

     /**

    * 字符串的日期格式的计算

    */

   public static int daysBetween(String smdate,String bdate) throws ParseException{

           SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");

           Calendar cal = Calendar.getInstance();

           cal.setTime(sdf.parse(smdate));

           long time1 = cal.getTimeInMillis();

           cal.setTime(sdf.parse(bdate));

           long time2 = cal.getTimeInMillis();

           long between_days=(time2-time1)/(1000*3600*24);

           return Integer.parseInt(String.valueOf(between_days));

   }

 }