custom category tree in wordpress

Hi i want to create a tree of categories in wordpress like this :

<ul>
    <a href=""> PARENT1 </a>
    <li><a href=""> CHILD 1-1</a></li>
    <li><a href=""> CHILD 1-2</a></li>
     .
     .
     .
</ul>
<ul>
    <a href=""> PARENT2 </a>
    <li><a href=""> CHILD 2-1</a></li>
    <li><a href=""> CHILD 2-2</a></li>
     .
     .
     .
</ul>

i want something that creates categories list in above format and show only categories which have children and hide those who don't

I Tried Something like this but it didn't give me what i wanted

<?php $args = array(
'type'                     => 'post',
'child_of'                 => 0,
'parent'                   => '',
'orderby'                  => 'name',
'order'                    => 'ASC',
'hide_empty'               => 0,
'hierarchical'             => 1,
'exclude'                  => '',
'include'                  => '',
'number'                   => '',
'taxonomy'                 => 'category',
'pad_counts'               => false 
);
$cats = get_categories( $args );
foreach( $cats as $cat) {
    if($cat->parent == 0) {
        $head = $cat->name;
        $cat_id = $cat->term_id;
    }
    echo "<a href=''>" . $head . "</a>";
    wp_list_cats("sort_column=NAME&optioncount=0&hierarchical=1&hide_empty=0&child_of={$cat_id}");
}

?>

Thanks For Your Response , I Found the Solution : This Code Works Fine

     $args = array(
            'type'                     => 'post',
            'child_of'                 => 0,
            'parent'                   => 0,
            'orderby'                  => 'name',
            'order'                    => 'ASC',
            'hide_empty'               => 1,
            'hierarchical'             => 0,
            'exclude'                  => '',
            'include'                  => '',
            'number'                   => '',
            'taxonomy'                 => 'category',
            'pad_counts'               => false 
            );
            $cats = get_categories( $args );
            foreach( $cats as $cat) {
                if($cat->parent == 0) {
                    $parent_cat = null;
                    $head = $cat->name;
                    $head_id = $cat->term_id;
                }
                echo "<ul><a class='parent-category' href=''>" . $head . "</a>";                                                    
                wp_list_cats("sort_column=NAME&optioncount=0&hierarchical=1&hide_empty=0&child_of={$head_id}&show_option_none=");
                echo "</ul>";
            }