JFolder::copy($src, $dest, $path, $force);

JFolder::create($path, $mode);

JFolder::move($src, $dest);

JFolder::exists($path);

JFolder::makeSafe($path);

JFolder::files($path, $filter = '.', $recurse, $fullpath , $exclude);

JFolder::folders($path, $filter = '.', $recurse, $fullpath , $exclude);

JFolder::listFolderTree($path, $filter, $maxLevel = 3, $level = 0, $parent = 0);

Array
(
    [0] => Array
        (
            [id] => 1
            [parent] => 0
            [name] => administrator
            [fullname] => g:/joomla_1012/administrator
            [relname] => g:/joomla_1012/administrator
        )
 
    [1] => Array
        (
            [id] => 2
            [parent] => 1
            [name] => backups
            [fullname] => g:/joomla_1012/administrator/backups
            [relname] => g:/joomla_1012/administrator/backups
        )
 
    [2] => Array
        (
            [id] => 3
            [parent] => 1
            [name] => components
            [fullname] => g:/joomla_1012/administrator/components
            [relname] => g:/joomla_1012/administrator/components
        )
)

<?php
// First we set up parameters.
$searchpath = JPATH_COMPONENT . '/images';
 
// Import the folder system library.
jimport('joomla.filesystem.folder');
 
// Then we create the subfolder called jpg.
if (!JFolder::create($searchpath . "/jpg"))
{
   // Throw error message and stop script.
}
 
// Now we read all jpg files and put them in an array.
$jpgFiles = JFolder::files($searchpath, '.jpg');
 
// Now we need some stuff from the ''JFile:: class'' to move all the files into the new folder.
foreach ($jpgFiles as $file)
{
   JFile::move($searchpath . '/' . $file, $searchpath . '/' . 'jpg' . $file);
}
 
// Last we move the complete subdir to the root of the component.
if (JFolder::move($searchpath . '/'. 'jpg', JPATH_COMPONENT))
{
   // Redirect with perhaps a happy message.
}
else
{
   // Throw an error.
}
?>