I'm angry at my friend for pretending to be interested in me
why would he pretend to be interested in you?
I know him, when he's bored,he pretends to be interested in other people.
Your anger is totally justifiable. It sounds like he is trying to get attention in any way he can and that may not end well.
Ok.
There are times where you have to decide if a person is worthy of your friendship. If they do things like this every time they are bored, it may be time to walk away.