JAvaは二次方程式ax^2+bx+c=0のクラスを設計する

public class QuadraticEquationtest //   
{
    public static void main(String[] args) 
    {
        //  a，b，c
        Quadraticequation equation1=new Quadraticequation(1.0,3,1);
        Quadraticequation.ret(equation1);
        Quadraticequation equation2=new Quadraticequation(1,2.0,1);
        Quadraticequation.ret(equation2);
        Quadraticequation equation3=new Quadraticequation(1,2,3);  
        Quadraticequation.ret(equation3);
    } 
}
class Quadraticequation
{
    private double a;
    private double b;
    private double c;
    public Quadraticequation(double x,double y,double z)//        
    {
        a=x;
        b=y;
        c=z;
    }
    public double getA()
    {
        return a;
    }
    public double getB()
    {
        return b;
    }
    public double getC()
    {
        return c;
    }
    public double getDiscriminant()
    {
        return b*b-4*a*c;
    } 
    public double getRoot1()
    {
        return (-b+Math.sqrt(getDiscriminant()))/(2*a);
    }
    public double getRoot2()
    {
        return (-b-Math.sqrt(getDiscriminant()))/(2*a);
    }
    public static void ret(Quadraticequation equation)//ret  ，      
    {
        double ret1=equation.getDiscriminant();
        if(ret1>0)
        {
            System.out.println("The equation has two roots "+equation.getRoot1()+" and "+equation.getRoot2());
        }
        else if(ret1==0)
        {
            System.out.println("The equation has one roots "+equation.getRoot1());
        }
        else
        {
            System.out.println("The equation has no real roots");
        }
    }
}