用一段代码记住一个知识点

Posted 2020-10-11

 1 public class Test_04 {
 2     public static void main(String[] args) {
 3         Scanner sc = new Scanner(System.in);
 4         Random r = new Random();
 5         System.out.println("请输入班级总组数:");
 6         int team = sc.nextInt();
 7         System.out.println("请输入每组人数:");        
 8         int member = sc.nextInt();
 9         //定义四个变量来记录全班的不及格数和,总分组最高平均分,全班平均分;
10         double result;
11         double max=0;
12         int fail=0;
13         int sum = 0;
14         //定义一个二维数组
15         int [][] arr =new int[team][member];
16         for(int j = 0;j<team;j++){
17                 int sum1=0;
18                 int fail1=0;
19                 double every=0;
20                 for (int i =0; i<member; i++){
21                     arr[j][i]=r.nextInt(101);
22                     
23                     if (arr[j][i]<=60){
24                         fail1++;
25                     }
26                     sum1+=arr[j][i];
27                     every = sum1/(member*1.0);
28                     max = max>every?max:every;
29                 }
30                 System.out.println("第"+(j+1)+"组不及格人数:"+fail1+‘\n‘+"第"+(j+1)+"组平均分:"+every);
31                 fail+=fail1;
32                 sum += sum1;
33         }
34         System.out.println("班级中单组最高平均分为:"+max);
35         System.out.println("班级中不及格人数为:"+fail);
36         //System.out.println("班级总平均分为:"+(sum/(team*member*1.0)));
37         result=(sum/(team*member*1.0));
38         String re =String.format("%.2f",result);
39         System.out.println("班级总平均分为:"+re);
40     }
41 }

View Code

其中 String re = String.format("%.2f",result);

运用String的函数完成小数点之后的精确输出.

此知识点我要牢牢记住,今天就给忘了.