When is it appropriate to use blank final variables?

Question

I was looking at another question about final variables and noticed that you can declare final variables without initializing them (a blank final variable). Is there a reaso

Answer 1

Blank final variables must be assigned "somewhere" in the constructor. A rather constructed example:

public class Test {
    final int sign;
    public Test(String upDown) {
        if (upDown.equals("up")) {
            sign = +1;
        } else {
            sign = -1;
        }
    }
}