// JAVA 中日期的处理
Calendar cal = Calendar.getInstance();
int month = cal.get(Calendar.MONTH);
// 上个月
cal.set(Calendar.MONTH, month - 1);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(sdf.format(cal.getTime()));
int maxDay = cal.getActualMaximum(Calendar.DATE);
System.out.println("maxDay " + maxDay);
 
可能的输出结果：
2008-12-01
maxDay 31

2009-02-16
maxDay 28