Java常用API(Math类）

 1 public class Test {
 2     public static void main(String[] args) {
 3       double a=-5.4;
 4         System.out.println("绝对值是："+Math.abs(a));
 5         System.out.println("向下取整："+Math.floor(a));
 6         System.out.println("向上取整："+Math.ceil(a));
 7         System.out.println("四舍五入："+Math.round(a));
 8 
 9     }
10 }