Math.Round() “四舍五入“方法

Math.Round(1.4) == 1
Math.Round(1.5) == 2
Math.Round(-1.5) == -2
Math.Round(-1.6) == -2

Math.Floor() “向下取整”
Math.Floor(1.4) == 1
Math.Floor(1.5) == 1
Math.Floor(-1.5) == -2
Math.Floor(-1.6) == -2

Math.Ceiling() “向上取整”
Math.Ceiling(1.4) == 2
Math.Ceiling(1.5) == 2
Math.Ceiling(-1.5) == -1
Math.Ceiling(-1.6) == -1

Math.Truncate() "取整“
Math.Truncate(1.4) == 1
Math.Truncate(1.5) == 1
Math.Truncate(-1.5) == -1
Math.Truncate(-1.6) == -1