java的日期时间操作

一，指定时间上的分钟操作

      public long addMinute(Date date, int minute){
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.MINUTE, minute);

 return cal.getTimeInMillis();

        public long addMinute(Date date, int minute){
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		cal.add(Calendar.MINUTE, minute);
		
		return cal.getTimeInMillis();
	}

 二，取当月1号

       public String getFirstDayOfMonth() {
     GregorianCalendar gCalendar = new GregorianCalendar();
     gCalendar.set(Calendar.DAY_OF_MONTH, 1);
     return dateToString(gCalendar.getTime(), "yyyy-MM-dd");
}

        public String getFirstDayOfMonth() {
		GregorianCalendar gCalendar = new GregorianCalendar();
		gCalendar.set(Calendar.DAY_OF_MONTH, 1);
		return dateToString(gCalendar.getTime(), "yyyy-MM-dd");
	}

 三，取上月1号

      public String getFirstDayOfLastMonth() {
 GregorianCalendar gCalendar = new GregorianCalendar();
 gCalendar.set(Calendar.DAY_OF_MONTH, 1);
 gCalendar.add(Calendar.MONTH, -1);
 return dateToString(gCalendar.getTime(),"yyyy-MM-dd");

        public String getFirstDayOfLastMonth() {
		GregorianCalendar gCalendar = new GregorianCalendar();
		gCalendar.set(Calendar.DAY_OF_MONTH, 1);
		gCalendar.add(Calendar.MONTH, -1);
		return dateToString(gCalendar.getTime(),"yyyy-MM-dd");
	}