Accessing specific class if condition is true

I'm making a trigonometry application with the different formulas for each shapes and such. What I wanted to know is: is there any way to make a boolean and access a specific class if this boolean is true?

Since I'm making Degree and Radian sub-classes, I needed to make it so when the boolean isInDegrees is true, it accesses Degree class, and the inverse if isInRadian is true.

You could use an if statement to test the boolean and do something if it is true
What do you mean by "access a class"?
call a method in a class
create an instance of a class