How to say "Of course not" in Japanese?
with example(s) please.

Question

Answer

「まさか。」

Example:
AとBは高校生です。
A：ねえ、日曜日の補習クラス、出席する？
B：まさか。
"Hey, are you gonna school on Sunday for the extra curricular class?"
"Of course not. "

Answer

Both "Of course not" and "Of course" are translated into 「もちろん」.
It depends on context: positive question or negative question.
When you wanna agree with the negative question, you have to answer with positive sentence.

Answer

もちろん好きではありません

Answer

もちろん好きではありません。 - Of course not.

「それはお好きではないでしょうね」「もちろん（好きではありません）」。- “You don't like it?”―“Of course not.” 
「君はヘビが好きですか」「もちろん好きではありません」- Do you like snakes? Of course not.
「野球は嫌いなんですね」「ええ嫌いです」- "Don't you like baseball?" - "Of course, not"