Java随机生成前N个不重复的整数

import java.io.BufferedOutputStream;  
import java.io.File;  
import java.io.FileNotFoundException;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.OutputStream;  
import java.util.Random;  
  
/** 
 * 测试随机生成前N个不重复的整数 
 * @author Administrator 
 * 
 */  
public class TestRandom {  
    public static void main(String[] args) {  
        randomNumber2File("e:/random.txt");  
    }  
      
    /** 
     * 根据提供的路径生成相应的随机数 
     * @param path 
     */  
    public static void randomNumber2File(String path){  
        File file = new File(path);  
        OutputStream os = null;  
        try {  
            os = new BufferedOutputStream(new FileOutputStream(file));  
            byte[] buf = new byte[20];  
            for(int j = 0; j < 100; j++){  
                int[] arr = ranInt(9);  
                StringBuffer sb = new StringBuffer();  
                for(int i = 0; i < arr.length; i++){  
                    sb.append(arr[i]);  
                }  
                sb.append("rn");  
                buf = sb.toString().getBytes();  
                os.write(buf);  
            }  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }finally{  
            if(null != os){  
                try {  
                    os.close();  
                } catch (IOException e) {  
                    // TODO Auto-generated catch block  
                    e.printStackTrace();  
                }  
            }  
        }  
    }  
      
    /** 
     * 利用随机生成数组的索引实现随机，并通过交换实现不重复 
     * @param n 
     * @return 
     */  
    public static int[] ranInt(int n) {  
        int[] arr = new int[n];  
        int i,randomIndex,temp;  
        for(i = 0; i < n; i++){  
            arr[i] = i+1;  
        }  
        for(i = 1; i < n; i++){  
            randomIndex = ranIndex(0,i);  
            //交换当前元素和生成的随机元素  
            temp = arr[i];  
            arr[i] = arr[randomIndex];  
            arr[randomIndex] = temp;  
        }  
        return arr;  
    }  
      
    public static int ranIndex(int start,int end){  
        Random r = new Random();  
        int result;  
        result = r.nextInt(end);  
        return result;    
    }  
}