给出日期（年月），怎么算出这个日期对应的前一个月和后一个月？

Question

            java.util.Calendar calendar = java.util.Calendar.getInstance();
           
            calendar.setTime(new Date());
            calendar.add(Calendar.DATE , -1);//这里前一天是负数，后一天是正数
            int year = calendar.get(Calendar.YEAR);
            int month = calendar.get(Calendar.MONTH) + 1;
            int day = calendar.get(Calendar.DAY_OF_MONTH);

Answer 1

Calendar cal1 = new GregorianCalendar(2004, Calendar.DECEMBER-1, 1);
Calendar cal2 = new GregorianCalendar(2004, Calendar.DECEMBER+1, 1);
    
System.out.println(""+cal1.get(Calendar.YEAR) +" "+ (cal1.get(Calendar.MONTH)+1));
System.out.println(""+cal2.get(Calendar.YEAR) +" "+ (cal2.get(Calendar.MONTH)+1));运行结果：
2004 11
2005 1