java.lang.Math静态方法和数学运算相关知识点

package math;
/*

• java.lang.Math 静态方法和数学运算相关

• double abs(double num)->取绝对值

• double ceil(double num)->向上取整

• double floor(double num)->向下取整

• long round(double num)->四舍五入

• Math.PI 圆周率 (double)
  */
  public class Demo01Math {

  public static void main(String[] args) {
  //取绝对值
  System.out.println(Math.abs(3.14));
  System.out.println(Math.abs(-2.5));

   //向上取整
   System.out.println(Math.ceil(3.9));//4
   System.out.println(Math.ceil(3.1));//4
   **System.out.println(Math.ceil(3.0));//3**
   
   //向下取整 抹零
   System.out.println(Math.floor(30.1));
   System.out.println(Math.floor(30.9));
   System.out.println(Math.floor(31.0));
   
   //四舍五入
   System.out.println(Math.round(20.4));
   System.out.println(Math.round(10.5));
  

  }