计算两个时间段相差几个月（包含相差的哪些月份）

实现思路：

　　通过Calendar类的before来判断两个日期是否符合前一个日期小于后一个日期。

　　实现：

        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();
        c1.set(2014, 9, 30);
        c2.setTime(new Date());
        System.out.println(c1.get(Calendar.YEAR)+" "+c1.get(Calendar.MONTH));
        while (c1.before(c2)) {
            int m = c1.get(Calendar.MONTH)+1;
            System.out.println(c1.get(Calendar.YEAR)+" "+(c1.get(Calendar.MONTH)+1));
            c1.add(Calendar.MONTH,1);
        }
        System.out.println(c1.get(Calendar.YEAR)+" "+(c1.get(Calendar.MONTH)+1));