Java调用外部程序

       ProcessBuilder builder = new ProcessBuilder();
       builder.command(commend);
       Process process = builder.start();
      final InputStream is1 = process.getInputStream();
      new Thread(new Runnable() {
             public void run() {
                     BufferedReader br = new BufferedReader(new InputStreamReader(is1));    
            try {
              while(br.readLine() != null) ;
             } catch (IOException e) {
               e.printStackTrace();
             }
             }
       }).start(); // 启动单独的线程来清空process.getInputStream()的缓冲区
       InputStream is2 = process.getErrorStream();
       BufferedReader br2 = new BufferedReader(new InputStreamReader(is2));    
       StringBuilder buf = new StringBuilder(); // 保存输出结果流
       String line = null;
      while((line = br2.readLine()) != null) buf.append(line);