Java 数学工具类Math

朱雀 2021-02-25 17:44 606阅读 0赞

## 数学工具类Math ##

>  *  java.util.Math 类是数学相关的工具类，里面提供了大量的静态方法，完成与数学运算相关的操作
>  *  `public static double abs(double num)`：获取绝对值
>  *  `public static double ceil(double num)`：向上取整
>  *  `public static double floor(double num)`：向下取整
>  *  `public static long round(double num)`：四舍五入

代码：

public class a32_数学工具类Math { 
        public static void main(String[] args) { 
    // 绝对值
            System.out.println(Math.abs(-2));
            System.out.println(Math.abs(2));
            System.out.println(Math.abs(0));
            System.out.println("---------");
    
    // 向上取整
            System.out.println(Math.ceil(8.2));
            System.out.println(Math.ceil(8.98));
            System.out.println(Math.ceil(2.3));
            System.out.println("---------");
    
    // 向下取整
            System.out.println(Math.floor(9.4));
            System.out.println(Math.floor(9.42));
            System.out.println(Math.floor(4.65));
            System.out.println("---------");
    
    // 四舍五入
            System.out.println(Math.round(5.6));
            System.out.println(Math.round(5.3));
            System.out.println(Math.round(4.9));
            System.out.println("---------");
    
    // 圆周率
            System.out.println(Math.PI);
        }
    }

![在这里插入图片描述][20200805175649118.png]

#### 练习 ####

**找出-10.8到5.9中绝对值大于6或小于2.1的整数**

public class a33_小学数学真题 { 
        public static void main(String[] args) { 
            double num01 = Math.ceil(-10.8);
            int num02 = (int)num01;
            int a = 0;
            for (int i = num02; i <= 5.9; i++){ 
                if (Math.abs(i) > 6 || Math.abs(i) < 2.1) { 
                    a++;
                }
            }
            System.out.println(a);
        }
    }

![在这里插入图片描述][20200805175500697.png]

[20200805175649118.png]: /images/1614275042076.png
[20200805175500697.png]: /images/1614275019166.png