数学工具类Math

package com.Demo06;
/*
java.util.Math类时数相关的工具类，里面提供了大量的静态方法，完成数学相关的操作
public static double abs(double num)：获取绝对值，有多种重载
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
Math.PI 代表近似的圆周率常量 （double）
 */
public class Demo01Math {
    public static void main(String[] args) {
        //绝对值
        System.out.println(Math.abs(0.1));   //0.1
        System.out.println(Math.abs(-0.1));  //0.1
        System.out.println(Math.abs(1));   //1
        //向上取整
        System.out.println(Math.ceil(2.1));    //3.0
        System.out.println(Math.ceil(2.9));    //3.0
        System.out.println(Math.ceil(2.0));    //2.0
        //向下取整
        System.out.println(Math.floor(3.1));   //3.0
        System.out.println(Math.floor(3.9));   //3.0
        System.out.println(Math.floor(3.0));   //3.0
        //四舍五入
        System.out.println(Math.round(4.4));   //4
        System.out.println(Math.round(4.9));   //5
        System.out.println(Math.round(4.5));   //5
    }
}