Java基础知识强化80：Math类概述与成员方法

1 public  static  final  double PI

1 public  static  final  double E

1 public static int abs(int a)：绝对值
2 public static double ceil(double a):向上取整
3 public static double floor(double a):向下取整
4 public static int max(int a,int b):最大值 (min自学)
5 public static double pow(double a,double b):a的b次幂
6 public static double random():随机数 [0.0,1.0)，0.0 <= x < 1.0
7 public static int round(float a) 四舍五入(参数为double的自学)
8 public static double sqrt(double a):正平方根    

 1 package cn.itcast_01;
 2 
 3 /*
 4  * Math:用于数学运算的类。
 5  * 成员变量：
 6  *         public static final double PI
 7  *         public static final double E
 8  * 成员方法：
 9  *         public static int abs(int a)：绝对值
10  *        public static double ceil(double a):向上取整
11  *        public static double floor(double a):向下取整
12  *        public static int max(int a,int b):最大值 (min自学)
13  *        public static double pow(double a,double b):a的b次幂
14  *        public static double random():随机数 [0.0,1.0)
15  *        public static int round(float a) 四舍五入(参数为double的自学)
16  *        public static double sqrt(double a):正平方根
17  */
18 public class MathDemo {
19     public static void main(String[] args) {
20         // public static final double PI
21         System.out.println("PI:" + Math.PI);
22         // public static final double E
23         System.out.println("E:" + Math.E);
24         System.out.println("--------------");
25 
26         // public static int abs(int a)：绝对值
27         System.out.println("abs:" + Math.abs(10));
28         System.out.println("abs:" + Math.abs(-10));
29         System.out.println("--------------");
30 
31         // public static double ceil(double a):向上取整
32         System.out.println("ceil:" + Math.ceil(12.34));
33         System.out.println("ceil:" + Math.ceil(12.56));
34         System.out.println("--------------");
35 
36         // public static double floor(double a):向下取整
37         System.out.println("floor:" + Math.floor(12.34));
38         System.out.println("floor:" + Math.floor(12.56));
39         System.out.println("--------------");
40 
41         // public static int max(int a,int b):最大值
42         System.out.println("max:" + Math.max(12, 23));
43         // 需求：我要获取三个数据中的最大值
44         // 方法的嵌套调用
45         System.out.println("max:" + Math.max(Math.max(12, 23), 18));
46         // 需求：我要获取四个数据中的最大值
47         System.out.println("max:"
48                 + Math.max(Math.max(12, 78), Math.max(34, 56)));
49         System.out.println("--------------");
50 
51         // public static double pow(double a,double b):a的b次幂
52         System.out.println("pow:" + Math.pow(2, 3));
53         System.out.println("--------------");
54 
55         // public static double random():随机数 [0.0,1.0)
56         System.out.println("random:" + Math.random());
57         // 获取一个1-100之间的随机数
58         System.out.println("random:" + ((int) (Math.random() * 100) + 1));
59         System.out.println("--------------");
60 
61         // public static int round(float a) 四舍五入(参数为double的自学)
62         System.out.println("round:" + Math.round(12.34f));
63         System.out.println("round:" + Math.round(12.56f));
64         System.out.println("--------------");
65         
66         //public static double sqrt(double a):正平方根
67         System.out.println("sqrt:"+Math.sqrt(4));
68     }
69 }