Thread: How to make calls to methods

Ok, in your evenSquares class, you have no constructor. What you do have is a method. So when you say new evenSquares(1000);, it is looking for a constructor that accepts an int.

So, there are a few ways to fix this with what you already have, depending on what you want to do:
If you want to create a constructor for your evenSquares class:

public class evenSquares {
 
  public evenSquares(int n){     //NOTICE: I took out the return type to make it a constructor
    for(int j = 2; j*j <= n; j += 2)
      System.out.println(j*j);
  }
}

OR

If you want to have an evenSquares class, with an evenSquares method (poor programming habit, but it will work):

public class evenSquaresDriver {
  public static void main(String[] args){
 
    evenSquares testsquare = new evenSquares();
    testsquare.evenSquares(1000);     //Using the empty constructor, and then calling the evenSquares(int) method
  }
}

You seem to not fully understand the difference between a method and a constructor. I suggest you do a little bit of reading about them to better understand how it works.

What class is the stringRoot(...) method in?

You are trying to create a new Object, of type stringRoot, and calling the new Object's stringRoot(...) method, which is clearly not what you are wanting to do.

ermmm, just do classname.stringRoot("1600")

don't think you need to make an object to use a classes method?