public static void main$($String$[]$ args$)\{$ BinaryTree tree $=$ new BinaryTree$()$;

$//$ Insert nodes

tree. insert $(1)$;

tree.insert $(2)$;

tree.insert $(3)$;

tree.insert $(4)$;

tree.insert $(5)$;

$//$ Print inorder traversal

tree.inorder$()$;

$\}$

$3$

This binary tree is $O2$ because each node has at most one child $($either left or right$).$

This binary tree is linear because each node has at most one child $($either left or right$).$

When we perform an inorder traversal, the nodes are visited in ascending order, demonstrating the linear structure of the tree

The following shows a method for inorder traversal private void inorderRec$($Node root$)\{$ if $($root $$ null$)\{$inorderRec$($root$.$left$)$; System.out.print$($root$.$data $+"")$; inorderRec$($root$.$right$)$; $\}\}.$