Math.ceil，Math.round，Math.floor区别
        //向上取整
        System.out.println("amt1=" + Math.ceil(71.01));        //四舍五入
        System.out.println("amt2=" + Math.round(71.01));        //向下取值,直接舍弃小数点
        System.out.println("amt3=" + Math.floor(71.01));

输出结果：
amt1=72.0
amt2=71
amt3=71.0