java.lang.IncompatibleClassChangeError：实现实用程序类

Question

我试图实现一个简单的矩形，但我得到了不兼容的类更改错误.. 期待非静态方法Utility.printLine（） 错误在线，

    util.printLine();

任何帮助??

完整的代码如下..

import java.lang.*;
import java.util.*;

class Rectangle
{

    private double height;
    private double width;

    public double getHeight()       
    {
        return height;
    }
    public double getWidth()
    {
        return width;
    }

    public void setHeight(double x) 
    {
        if(x<=0)
        {
            System.out.println("Invalid Height");
            System.exit(0);
        }
        else
        {
            height = x;
        }
    }

    public void setWidth(double x)
    {
        if(x<=0)
        {
            System.out.println("Invalid Width");
            System.exit(0);
        }
        else
        {
            width = x;
        }
    }

    public double getArea()
    {
        double a;
        a = height*width;
        return a;
    }
    public double getPerimeter()
    {
        double p;
        p = 2*(height+width);
        return p;
    }
}


class Utility
{
    public  void printLine()
    {
        for(int i=1;i<=40;i++)
        {
            System.out.print("=");
        }
        System.out.println();
    }
    public  void printLine(char ch)         
    {
        for(int i=1;i<=40;i++)
        {
            System.out.print(ch);
        }
        System.out.println();
    }
    public  void printLine(char ch, int x)          
    {
        for(int i=1;i<=x;i++)
        {
            System.out.print(ch);
        }
        System.out.println();
    }
}

class RectTest7
{
    public static void main(String args[])
    {
        double area, peri, x;

        Rectangle r = new Rectangle();
        Scanner input = new Scanner(System.in);
        Utility util = new Utility();

        System.out.print("Enter height : ");
        x = input.nextDouble();

        r.setHeight(x);

        System.out.print("Enter width : ");
        x = input.nextDouble();

        r.setWidth(x);

        area = r.getArea();
        peri = r.getPerimeter();

        util.printLine();
        System.out.println("Height : "+r.getHeight());
        util.printLine();
        System.out.println("Width : "+r.getWidth());
        util.printLine();
        System.out.println("Area : "+area);
        util.printLine();
        System.out.println("Perimeter : "+peri);
        util.printLine();

        r = null;
    }
}