Math类中round(), ceil(), floor()方法

1.round(a)
a+0.5，然后向下取整。如果a是float类型，返回int；如果a是double类型，返回long。

• Math.round(-5.6) = - 6
• Math.round(-5.4) = - 5
• Math.round(-5.5) = - 5
• Math.round(5.6) = 6
• Math.round(5.5) = 6
• Math.round(5.4) = 5

2.ceil(b)
向上取整，b为double，返回double

• Math.ceil(-5.5) = - 5.0
• Math.ceil(-5.4) = - 5.0
• Math.ceil(-5.6) = - 5.0
• Math.ceil(5.5) = 6.0
• Math.ceil(5.6) = 6.0
• Math.ceil(5.4) = 6.0

3.floor(x)
向下取整，x为double，返回double

• Math.ceil(-5.5) = - 6.0
• Math.ceil(-5.4) = - 6.0
• Math.ceil(-5.6) = - 6.0
• Math.ceil(5.5) = 5.0
• Math.ceil(5.6) = 5.0
• Math.ceil(5.4) = 5.0

4.如有错误，望大佬不吝赐教！感激~