java 发作不重复的随机数

java 产生不重复的随机数

import java.io.*;

public class test
{
?public static void main (String [] str)
?{
?? final int num = 20;
??
??int Random[] = new int[num];
??for(int i = 0 ; i < num ; i++)
??{
??//?int ran=-1;
???while(true)
???{
????int ran = (int)(num*Math.random());
????for(int j = 0 ; j < i ; j++)
????{
?????if(Random[j] == ran)
?????{
??????ran = -1;
??????break;
?????}?
????}
????if(ran != -1)
????{
?????Random[i] = ran;
?????break;
????}
????
???}
???
??}
??for(int i = 0 ; i < num ; i ++)
??{
???System.out.print(Random[i]+",");
??}
?}
}