Error Passing Value Of A Variable From One Class To Main Method Of Another Class

I've 3 classes.

1. Circle
2. GetInputFromUser
3. testCircle

package ABC;
public class Circle {
private double radius;
public double getRadius() {
return radius;

[Code] .....

In the testCircle class, in the line: getRadius = ui1.GetInput();

It's showing the error: The method GetInput(float) in the type GetInputFromUser is not applicable for the arguments ()

And when I do: getRadius = ui1.GetInput(rad);

It's showing the error: rad cannot be resolved