Convert Sorted Array to Binary Search Tree

public static TreeNode sortedArrayToBST( int[] nums ) {
    return helper( nums, 0, nums.length - 1 );
}
private static TreeNode helper( int[] nums, int low, int high ) {
    if( low > high ) return null;
    if( low == high ) return new TreeNode( nums[low] );
    int mid = low + ( high - low ) / 2;
    TreeNode root = new TreeNode( nums[mid] );
    root.left = helper( nums, low, mid - 1 );
    root.right = helper( nums, mid + 1, high );
    return root;
}