float a = 3.933f;
System.out.println(Math.rint(a));//四捨五入型,返回是個double型的值
System.out.println(Math.round(a));//四捨五入，返回是double型的值
System.out.println(Math.ceil(a));//向上取整，返回大於double數值最小的數，double型
System.out.println(Math.floor(a));//向下取整，返回小於double數值最大的數，double型