Java>常用API>>数学工具类Math

package 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***算相关的操作。
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
 */
public class Demo01Math {
    public static void main(String[] args) {
        //获取绝对值
        System.out.println(Math.abs(-3.52)); //3.52
        System.out.println(Math.abs(0)); //0
        System.out.println(Math.abs(6.2)); //6.2
        System.out.println("=======================");
 
        //向上取整
        System.out.println(Math.ceil(3.9)); //4.0
        System.out.println(Math.ceil(3.1)); //4.0
        System.out.println(Math.ceil(3.0)); //3.0
        System.out.println("=======================");
 
        //向下取整
        System.out.println(Math.floor(3.9)); //3.0
        System.out.println(Math.floor(3.1)); //3.0
        System.out.println(Math.floor(3.0)); //3.0
        System.out.println("=======================");
 
        //四舍五入
        System.out.println(Math.round(3.4)); //3
        System.out.println(Math.round(3.6)); //4
        System.out.println(Math.round(3.0)); //3
        System.out.println("=======================");
 
        //圆周率
        System.out.println(Math.PI); //3.14159265358979
    }
}

3.52
0
6.2
=======================
4.0
4.0
3.0
=======================
3.0
3.0
3.0
=======================
3
4
3
=======================
3.141592653589793