java随机数的产生

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1. import java.util.*;
2.(A) public class Test
       { public static void main(String[] args)
         {
         //生成 [0-n) 个不重复的随机数 st 用来保存这些随机数
         ArrayList list = new ArrayList();
         int n = 10;
         Random rand = new Random();
         boolean[] bool = new boolean[n];
         int num =0;
         for (int i = 0; i<n; i++)
                 {
               do{//如果产生的数相同继续循环
                 num = rand.nextInt(n);
             }while(bool[num]);
             bool[num] =true;
             list.add(num);
         }
         System.out.println (list);
   }
(B)
   public class Test
{
    public static void main(String[] args)
     {
         int[] arr = new int[10];
         for (int i = 0; i < 10; i++)
         {
             arr[i] = (int) (Math.random() * 40) + 1;
             for (int j = 0; j < i; j++)
             {
                 if (arr[j] == arr[i])
                 {
                     i--;
                        break;
                 }
             }
       }
         for (int i = 0; i < 10; i++)
             System.out.print(arr[i] + " ");
     }
}
(C)Java code

import   java.util.*;
public   class   Test
{

         public   static   void   main(String[]   args)
         {
                 int   n=40;
                 int[]   num   =   new   int[n];
                 for(int   i=0;i <num.length;i++)
                         num[i]   =   i+1;

                 int[]   arr   =   new   int[10];
                for(int   i=0;i <arr.length;i++)
                 {
                        int   r   =(int)(Math.random()*n);
                         arr[i]=num[r];
                         num[r]=num[n-1];
                         n--;
                 }
                 for(int   i=0;i <arr.length;i++)
                         System.out.print(arr[i]+"   ");
         }
}

(D)Java code
import   java.util.*;
public   class   Test
{

         public   static   void   main(String[]   args)
         {
                 LinkedList <Integer>   myList=   new   LinkedList <Integer> ();
                 int   n=40;
                 for(int   i=0;i <n;i++)
                         myList.add(i+1);
                 int[]   arr   =   new   int[10];
                 for(int   i=0;i <arr.length;i++)
                 {
                         arr[i]=myList.remove((int)(Math.random()*n));
                         n--;
                 }
                 for(int   i=0;i <arr.length;i++)
                 {
                         System.out.print(arr[i]+"   ");
                 }
         }
}

(E)Java code

import   java.util.*;
public   class   Test
{

         public   static   void   main(String[]   args)
         {
                 Set <Integer>   mySet   =   new   LinkedHashSet <Integer> ();
                 while(mySet.size() <10)
                 {
                         mySet.add((int)(Math.random()*40+1));
                 }
                 for(Integer   i:mySet)
                {
                        System.out.print(i+"   ");
                 }
         }
}