1.Math.ceil() 向上取整
System.out.println(Math.ceil(3.4)); //输出4 System.out.println(Math.ceil(3.7)); //输出4 System.out.println(Math.ceil(-3.4)); //输出-3 System.out.println(Math.ceil(-3.7)); //输出-3
2.Math.floor() 向下取整
System.out.println(Math.floor(3.4)); //输出3 System.out.println(Math.floor(3.7)); //输出3 System.out.println(Math.floor(-3.4)); //输出-4 System.out.println(Math.floor(-3.7)); //输出-4
3.Math.round() 四舍五入【特别注意:负数的五入是向大的数入)
记忆法则:将原有的数加上0.5之后再向下取整
System.out.println(Math.round(3.4)); //输出3 System.out.println(Math.round(3.7)); //输出4 System.out.println(Math.round(-3.4)); //输出-3 System.out.println(Math.floor(-3.7)); //输出-4 System.out.println(Math.floor(-3.5)); //输出-3
4.补充:int() 去零,不管后面大于5还是小于5,都要去掉
System.out.println(Math.int(3.4)); //输出3 System.out.println(Math.int(3.7)); //输出3 System.out.println(Math.int(-3.4)); //输出-3 System.out.println(Math.int(-3.7)); //输出-3