How to implement file copy through byte buffer stream in java

/**
   * 通过字节缓冲流实现文件的拷贝
   *
   * @param sourcePath 源文件路径
   * @param targetPath 目标文件路径
   */
  public static void copyFileByBuffered(String sourcePath, String targetPath){
    //源文件路径
    File source = new File(sourcePath);
    //目标文件路径
    File target = new File(targetPath);

    //如果源文件不存在则不能拷贝
    if (!source.exists()) {
      return;
    }
    //如果目标文件目录不存在则创建
    if (!target.getParentFile().exists()) {
      target.getParentFile().mkdirs();
    }

    InputStream in = null;
    OutputStream out = null;
    try {
      //字节缓冲输入流和字节缓冲输出流
      in = new BufferedInputStream(new FileInputStream(source));
      out = new BufferedOutputStream(new FileOutputStream(target));

      byte[] b = new byte[1024];
      int temp = 0;
      //每次读取一个1024的字节数组
      while((temp = in.read(b)) != -1){
        //输出到文件
        out.write(b,0,temp);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }finally {
      //关闭流
      try {
        if (in != null) {
          in.close();
        }
        if (out != null) {
          out.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }