I'm relatively new to java, and really new to the concept of classes
and their applications. I managaged to get through a few exercises
(largely based off of examples) and now I'm stuck on the main method of
a new exercise. I feel I don't fully understand how to "apply" methods
from classes. I was hoping someone could enlighten me(maybe
particularly how to use constructors in the main method). Any help
would be greatly appreciated.

Here's my class

class Question2 { //aka Circle
 private int radius;
 private double circumference;

public Question2 (int radius) {
   this.radius = radius;
   circumference = 2 * Math.PI * radius;
 }

public double getCirc() {
   return circumference;
 }

}

And here's my main method

import java.util.*;
class Q2Main {

 public static void main (String args[]) {
   int radius;
   Question2 smallCircle, largeCircle;

   //compute circumference of a smaller circle
   smallCircle = new Question2();
   Scanner input = new Scanner(System.in);
    System.out.println("Enter the radius of the Smaller Circle");
   radius = input.nextInt();
   smallCircle.getCirc();

   //compute circumference of a larger circle
   largeCircle = new Question2();
      System.out.println("Enter the radius of the Larger Circle");
   radius = input.nextInt();
   largeCircle.getCirc();

   //Display the difference
   System.out.println("Difference in circumference of two circles");
   System.out.println("Circumference of smaller circle: " +
smallCircle);
   System.out.println("circumference of larger circle: " +
largeCircle);
   System.out.println("Difference: " + (largeCircle - smallCircle));
 }
}

And here's the errors I get;

cannot find symbol contructor Question2()
cannot find symbol contructor Question2()
Operator cannot be applied to Question2(), Question2()