wordpress - list main terms and sub terms under it

list main terms and sub terms under it

<?php
//list terms in a given taxonomy
$taxonomy = 'apptypes';
$appargs=array(
  'hide_empty' => false,
  'orderby' => 'name',
  'order' => 'ASC',
  'parent' => '0'
);
$appterms = get_terms($taxonomy,$appargs);
?>
<ul>
<?php
foreach ($appterms as $appterm) {
echo '<li>' . '<a href="' . esc_attr(get_term_link($appterm, $taxonomy)) . '" title="' . sprintf( __( "View all posts in %s" ), $appterm->name ) . '" ' . '>' . $appterm->name.'</a></li>';
$termID = $appterm->term_id;
$taxonomyName = $taxonomy;
$termchildren = get_term_children( $termID, $taxonomyName );
foreach ($termchildren as $child) {
	$termsub = get_term_by( 'id', $child, $taxonomyName );
	echo '<ul>';
	echo '<li>'.$termsub->name.'</li>';
	echo '</ul>';
} }
?>
</ul>