Java隨機生成前N個不重復的整數

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;

/**

測試隨機生成前N個不重復的整數 
@author Administrator 
*/

public class TestRandom {

 public static void main(String[] args) {

 randomNumber2File("e:/random.txt");  

}
/**

根據提供的路徑生成相應的隨機數 
@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("\r\n");  
     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();  
     }  
 }  

}

}
/**

利用隨機生成數組的索引實現隨機，并通過交換實現不重復 
@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);  
 //交換當前元素和生成的隨機元素  
 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;

}

}  </pre>