float a = 3.933f;
System.out.println(Math.rint(a));//四舍五入型,返回是个double型的值
System.out.println(Math.round(a));//四舍五入，返回是double型的值
System.out.println(Math.ceil(a));//向上取整，返回大于double数值最小的数，double型
System.out.println(Math.floor(a));//向下取整，返回小于double数值最大的数，double型