public final class Math extends Object
public static double floor(double a)
public static long round(double a)
public static int round(float a)
public static double ceil(double a)
floor 返回不大于的最大整数;
ceil 则是不小于他的最小整数;
round 它表示“四舍五入”，算法为Math.floor(x+0.5)，即将原来的数字加上0.5后再向下取整;
所以，Math.round(11.5)的结果为12，Math.round(-11.5)的结果为-11;
| Math.floor | Math.round | Math.ceil | |
|
1.4
|
1.0
|
1
|
2.0
|
|
1.5
|
1.0
|
2
|
2.0
|
|
1.6
|
1.0
|
2
|
2.0
|
|
-1.4
|
-2.0
|
-1
|
-1.0
|
|
-1.5
|
-2.0
|
-1
|
-1.0
|
|
-1.6
|
-2.0
|
-2
|
-1.0
|