已知源目录路径sourceFilePath,此目录下还有多级子目录和多个文本文件(*.txt)。尝试编写一个方法，将此目录下所有的文件拷贝至另一个目录targetFilePath，并其中的文本文件修改成SQL文件(*.SQL)。

public void copyFolder(String oldPath, String newPath) {

         try {

            (new File(newPath)).mkdirs(); // 如果文件夹不存在 则建立新文件夹

            File fileTemp = new File(oldPath);

            String[] file = fileTemp.list();

            File temp = null;

            for (int i = 0; i < file.length; i++) {

               if (oldPath.endsWith(File.separator)) {

                   temp = new File(oldPath + file[i]);

               } else {

                   temp = new File(oldPath + File.separator + file[i]);

               }

               if (temp.isFile()) {

                    FileInputStream input = new FileInputStream(temp);

                    if (file[i].endsWith(".txt")) {

                       temp = new File(oldPath + File.separator + file[i].substring(0, file[i].length() - 4) + ".sql");

                   }

                   FileOutputStream output = new FileOutputStream(newPath + "/" + (temp.getName()).toString());

                   byte[] b = new byte[1024 * 5];

                   int len;

                   while ((len = input.read(b)) != -1) {

                       output.write(b, 0, len);

                   }

                   output.flush();

                   output.close();

                   input.close();

              }

              if (temp.isDirectory()) { // 如果是子文件夹

                   copyFolder(oldPath + "/" + file[i], newPath + "/" + file[i]);

              }

         }

       } catch (Exception e) {

          System.out.println("复制整个文件夹内容操作出错");

          e.printStackTrace();

       }

}