I don't get it!

The error I get is "call to this must be first statement in constructor" its referring to "this(4,4,4)" EDIT: Constructors don't have a return type lol -_-

public class Circle {
    public double x;
    public double y;
    public double radius;

    public void Circle(double x, double y, double radius){
        this.x = x;
        this.y = y;
        this.radius = radius;
    }
    public void Circle(double x){
        this.x = x;
        this.y = 5;
        this.radius = 5;
    }
    public void Circle(double x, double y){
        this.x = x;
        this.y = y;
        this.radius = 5;
    }
    public void Circle(){
        this(4, 4, 4);
    }

    public static void main(String[] args) {

    }
}