java 日期相关

获取本月第一天

	public Date firstDayOfMonth(Date date){
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		cal.set(Calendar.DAY_OF_MONTH, 1); 
		return cal.getTime();
	}

获取本月最后一天

	public Date lastDayOfMonth(Date date) {
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		cal.set(Calendar.DAY_OF_MONTH, 1);
		cal.roll(Calendar.DAY_OF_MONTH, -1);
		return cal.getTime();
	}
	public Date lastDayOfMonth2(Date date) {
		Calendar cal = Calendar.getInstance();
		cal.setTime(date);
		int value = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
		cal.set(Calendar.DAY_OF_MONTH, value);
		return cal.getTime();
	}