java 快速求素数

 package test ;
 import java.util.Scanner ;
 public class hello
 {
     public static void main(String [] args)
     {
         Scanner read = new  Scanner(System.in);
         while(read.hasNext())
         {
         String rr = read.next();
         int maxn=Integer.parseInt(rr);
         boolean isprime[] = new boolean [maxn] ; //Java 默认初始化值为false
     //    int prime[] =new int [maxn/3];
         int i,j;
         for( i=2 ; i<maxn ; i++ )
         {
             if(!isprime[i])
             {
                 for(j=i+i ;j<maxn ;j+=i)
                        isprime[j]=true;
             }
         }
        for(i=2 ;i<maxn ;i++)
        {
            if(!isprime[i])
           System.out.print(" "+i);
        }
       System.out.println();
     }
     }
 }