Untitled

public class Circles {
    private double a;
    private final double b = 0;
    private double x;
    private double y;

    public Circles(double a, double x, double y) {
        this.a = a;
        this.x = x;
        this.y = y;
    }

    double calcR() {
        return Math.sqrt((x - a) * (x - a) + (y - b) * (y - b));
    }

    double lengthCircle(){
        return calcR()*2 * Math.PI;
    }
}