Detect sides of player touch blocks

How can I check if any part of the sides of the player's hitbox (the front, back, left and right of the player), but not the bottom or the top, are touching non-air blocks?

 

Get the direction the player is looking in then check all sides for non air blocks

 

How do I check sides? And why do I need to get the direction first?

 

You might want to look into this: https://www.spigotmc.org/threads/get-size-of-an-entitys-bounding-box-hitbox.105100/

 

@NoobDoesMC first id say tell us what you actually want to achieve. Why do you need blocks in hitbox face directions.
@MattTheBeast s idea was quiet good. With the players location, his viewing direction and a bit of cross product you should get locations that resemble the different faces of his hitbox. But guess its better if you start off with your idea in detail.