代码：

// 获得一月前的日期
public String lastMonth() {
	Date date = new	Date();
	int year = Integer.parseInt(new	SimpleDateFormat("yyyy").format(date));
	int month = Integer.parseInt(new SimpleDateFormat("MM").format(date)) -	1;
	int day	= Integer.parseInt(new SimpleDateFormat("dd").format(date));
	if (month == 0)	{
		year -=	1;
		month =	12;
	} else if (day > 28) {
		if (month == 2)	{
			if (year % 400 == 0 || (year % 4 == 0 && year %	100 != 0)) {
				day = 29;
			} else
				day = 28;
		} else if ((month == 4 || month	== 6 ||	month == 9 || month == 11)
				&& day == 31) {
			day = 30;
		}
	}
	String y = year	+ "";
	String m = "";
	String d = "";
	if (month < 10)
		m = "0"	+ month;
	else
		m = month + "";
	if (day	< 10)
		d = "0"	+ day;
	else
		d = day	+ "";

	return y + "-" + m + "-" + d;
}