月第一天和最后一天的计算(试一试语法着色功能)

//  本月的第一天
   Calendar calendar  =   new  GregorianCalendar();
   calendar.set( Calendar.DATE,  1 );
   SimpleDateFormat simpleFormate  =   new  SimpleDateFormat( " yyyy-MM-dd " );
   System.out.println(simpleFormate.format(calendar.getTime()));
  
   // 本月的最后一天
   Calendar calendar  =   new  GregorianCalendar();
   calendar.set( Calendar.DATE,  1 );
   calendar.roll(Calendar.DATE,  - 1 );
   SimpleDateFormat simpleFormate  =   new  SimpleDateFormat( " yyyy-MM-dd " );
   System.out.println(simpleFormate.format(calendar.getTime()));